U.S. patent number 6,096,468 [Application Number 09/325,711] was granted by the patent office on 2000-08-01 for toner, toner production process, and image forming method.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Yasukazu Ayaki, Satoshi Handa, Akira Hashimoto, Keiji Komoto, Manabu Ohno.
United States Patent |
6,096,468 |
Ohno , et al. |
August 1, 2000 |
**Please see images for:
( Certificate of Correction ) ** |
Toner, toner production process, and image forming method
Abstract
A toner for use in development of electrostatic latent images is
disclosed. The toner has toner particles containing a binder resin,
a colorant, a wax and a compound of Formula (A): ##STR1## wherein
R.sub.1 and R.sub.4 each represent a substituted or unsubstituted
aromatic group, inclusive of a condensed ring; R.sub.2 and R.sub.3
each represent a hydrogen atom, an alkyl group, a substituted or
unsubstituted aromatic group, inclusive of a condensed ring; M
represents an element selected from B, Ti, Fe, Co, Cr, Al and Ni;
and X.sup.n+ represents a cation. The toner has the shape factors
SF-1 and SF-2 with the specified range. Further, disclosed are a
process for producing the toner and an image forming method using
the toner.
Inventors: |
Ohno; Manabu (Numazu,
JP), Handa; Satoshi (Shizuoka-ken, JP),
Hashimoto; Akira (Numazu, JP), Komoto; Keiji
(Numazu, JP), Ayaki; Yasukazu (Numazu,
JP) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JP)
|
Family
ID: |
26456762 |
Appl.
No.: |
09/325,711 |
Filed: |
May 4, 1999 |
Foreign Application Priority Data
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Jun 5, 1998 [JP] |
|
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10-156999 |
Apr 27, 1999 [JP] |
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11-118931 |
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Current U.S.
Class: |
430/108.3;
430/108.4; 430/110.3; 430/110.4; 430/123.5; 430/137.17 |
Current CPC
Class: |
G03G
9/0819 (20130101); G03G 9/09783 (20130101); G03G
9/0827 (20130101); G03G 9/0825 (20130101) |
Current International
Class: |
G03G
9/097 (20060101); G03G 9/08 (20060101); G03G
009/097 (); G03G 013/22 () |
Field of
Search: |
;430/110,111,124,126,137 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
0658816 |
|
Jun 1995 |
|
EP |
|
0791861 |
|
Aug 1997 |
|
EP |
|
36-10231 |
|
Jul 1961 |
|
JP |
|
56-13945 |
|
Apr 1981 |
|
JP |
|
59-53856 |
|
Mar 1984 |
|
JP |
|
59-61842 |
|
Apr 1984 |
|
JP |
|
2-221967 |
|
Sep 1990 |
|
JP |
|
3-39973 |
|
Feb 1991 |
|
JP |
|
5-72812 |
|
Mar 1993 |
|
JP |
|
5-61257 |
|
Mar 1993 |
|
JP |
|
5-165257 |
|
Jul 1993 |
|
JP |
|
6-301240 |
|
Oct 1994 |
|
JP |
|
10-90946 |
|
Apr 1998 |
|
JP |
|
10-312089 |
|
Nov 1998 |
|
JP |
|
Other References
Patent Abstracts of Japan, vol. 18, No. 21 (P-1674); 194 for J.P.
05-257324. .
Patent Abstracts of Japan, vol. 15, No. 511 (P-1292), Dec. 1991,
for JP 03-221967. .
Patent Abstracts of Japan, vol. 98, No. 3, Feb. 1998 for JP
09-288383..
|
Primary Examiner: Martin; Roland
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper &
Scinto
Claims
What is claimed is:
1. A toner comprising toner particles containing at least a binder
resin, a wax and a compound represented by Formula (A): ##STR46##
wherein R.sub.1 and R.sub.4 each represent a substituted or
unsubstituted aromatic group, inclusive of a condensed ring;
R.sub.2 and R.sub.3 each represent a hydrogen atom, an alkyl group,
a substituted or unsubstituted
aromatic group, inclusive of a condensed ring; M represents an
element selected from B, Ti, Fe, Co, Cr, Al and Ni; and X.sup.n+
represents a cation,
said toner having shape factors SF-1 and SF-2 with a value of
100<SF-1.ltoreq.160 and a value of 100<SF-2.ltoreq.140.
2. The toner according to claim 1, wherein the shape factor SF-1 is
100<SF-1.ltoreq.150 and the shape factor SF-2 is
100<SF-2.ltoreq.130.
3. The toner according to claim 1, wherein the shape factor SF-1 is
100<SF-1.ltoreq.140 and the shape factor SF-2 is
100<SF-2.ltoreq.120.
4. The toner according to claim 1, wherein the ratio of the shape
factor SF-1 to the shape factor SF-2, (SF-2)/(SF-1), is in a value
of 1 or less.
5. The toner according to claim 1, which has an average circularity
of from 0.920 to 0.995 and a circularity standard deviation of less
than 0.040 in its circularity frequency distribution as measured
with a flow type particle image analyzer.
6. The toner according to claim 1, which has an average circularity
of from 0.950 to 0.995 and a circularity standard deviation of less
than 0.040 in its circularity frequency distribution as measured
with a flow type particle image analyzer.
7. The toner according to claim 1, which has an average circularity
of from 0.970 to 0.990 and a circularity standard deviation of from
0.015 to less than 0.035 in its circularity frequency distribution
as measured with a flow type particle image analyzer.
8. The toner according to claim 1, wherein a toner having an
average circularity less than 0.950 in its circularity frequency
distribution is in a content of 15% by number or less.
9. The toner according to claim 1, which has a weight-average
particle diameter of from 4 .mu.m to 9 .mu.m.
10. The toner according to claim 1, which has a coefficient of
variation in number distribution, of 30 or less.
11. The toner according to claim 1, wherein a toner fine powder
having particle diameters of 4.00 .mu.m or smaller in number
distribution is in a content not more than 25% by number.
12. The toner according to claim 1, which has a weight-average
particle diameter of from 4 .mu.m to 9 .mu.m, has a coefficient of
variation in number distribution, of 30 or less, and has a toner
fine powder having particle diameters of 4.00 .mu.m or smaller in
number distribution in a content not more than 25% by number.
13. The toner according to claim 1, which has a weight-average
particle diameter of from 4 .mu.m to 9 .mu.m, has a coefficient of
variation in number distribution, of 25 or less, and has a toner
fine powder having particle diameters of 4.00 .mu.m or smaller in
number distribution in a content not more than 20% by number.
14. The toner according to claim 1, wherein said wax is dispersed
in the form of substantially a spherical or spindle-shaped island
or islands in such a way that, when in cross-sectional observation
of toner particles on a transmission electron microscope (TEM);
(1) twenty planes of cross sections of toner particles having
length R (.mu.m) satisfying the relation of
0.9.ltoreq.R/D4.ltoreq.1.1 with respect to weight-average particle
diameter D4 (.mu.m) are picked up; and
(2) each length r of the largest among phase-separated structures
ascribable to the wax present in the cross-sectional plane of the
toner particles thus picked up is measured;
the arithmetic mean value of r/R, (r/R).sub.st, thus determined
satisfies:
15. The toner according to claim 14, wherein the (r/R).sub.st
satisfies:
16. The toner according to claim 1, wherein said wax has a maximum
endothermic peak at from 50.degree. C. to 100.degree. C. at the
time of temperature rise, in the DSC curve as measured with a
differential scanning calorimeter.
17. The toner according to claim 1, wherein said wax is an ester
wax having ester compounds satisfying the following general
formula:
wherein R.sub.1 and R.sub.2 each represent a hydrocarbon group
having 15 to 45 carbon atoms.
18. The toner according to claim 17, wherein said ester wax
contains ester compounds having the same number of carbon atoms in
total, in an amount of from 50% by weight to 95% by weight.
19. The toner according to claim 1, which contains an inorganic
fine powder.
20. The toner according to claim 19, wherein said inorganic fine
powder has been treated with silicone oil.
21. The toner according to claim 1, which is negatively
chargeable.
22. The toner according to claim 1, wherein said compound
represented by Formula (A) is contained in an amount of from 0.1
part by weight to 10 parts by weight based on 100 parts by weight
of the binder resin.
23. The toner according to claim 1, wherein said compound
represented by Formula (A) is contained in an amount of from 0.6
part by weight to 5 parts by weight based on 100 parts by weight of
the binder resin.
24. The toner according to claim 1, wherein said toner particles
are obtained by subjecting a polymerizable monomer composition
containing a polymerizable monomer, the wax and the compound
represented by Formula (A), to suspension polymerization in an
aqueous medium.
25. The toner according to claim 24, wherein said compound
represented by Formula (A) is added in an amount of from 0.1 part
by weight to 10 parts by weight based on 100 parts by weight of the
polymerizable monomer.
26. The toner according to claim 24, wherein the compound
represented by Formula (A) is added in an amount of from 0.6 part
by weight to 5 parts by weight based on 100 parts by weight of the
polymerizable monomer.
27. A process for producing a toner, comprising;
a granulation step of dispersing in an aqueous medium a
polymerizable monomer composition containing at least a
polymerizable monomer, a colorant, a wax, a polymerization
initiator and a compound represented by Formula (A): ##STR47##
wherein R.sub.1 and R.sub.4 each represent a substituted or
unsubstituted aromatic group, inclusive of a condensed ring;
R.sub.2 and R.sub.3 each represent a hydrogen atom, an alkyl group,
a substituted or unsubstituted aromatic group, inclusive of a
condensed ring; M represents an element selected from B, Ti, Fe,
Co, Cr, Al and Ni; and X.sup.n+ represents a cation, to form
particles of the polymerizable monomer composition; and
a polymerization step of polymerizing the polymerizable monomer
present in the particles of the polymerizable monomer composition
to form toner particles;
the reaction to polymerize the polymerizable monomer in the course
of from the granulation step to the polymerization step being
carried out while keeping the pH of the aqueous medium at 4.5 to
8.5, until the polymerization conversion of the polymerizable
monomer comes to be 10% or more; and
the toner having shape factors SF-1 and SF-2 with a value of
100<SF-1.ltoreq.160 and a value of 100<SF-2.ltoreq.140.
28. The process according to claim 27, wherein said reaction to
polymerize the polymerizable monomer in the course of from the
granulation step to the polymerization step is carried out while
keeping the pH of the aqueous medium at 4.5 to 6.0, until the
polymerization conversion of the polymerizable monomer comes to be
10% or more.
29. The process according to claim 27, wherein, after the
polymerization conversion of the polymerizable monomer is made
higher to 10% or more by the reaction to polymerize the
polymerizable monomer in the course of from the granulation step to
the polymerization step, the pH of the aqueous medium is adjusted
to 9 to 13 to make the polymerization conversion still higher.
30. An image forming method comprising:
a charging step of applying a voltage to a charging member from the
outside to charge an electrostatic latent image bearing member;
a latent image forming step of forming an electrostatic latent
image on the electrostatic latent image bearing member thus
charged;
a developing step of developing the electrostatic latent image by
the use of a toner to from a toner image on the electrostatic
latent image bearing member;
a transfer step of transferring the toner image formed on the
electrostatic latent image bearing member, to a transfer medium
with or without intervention of an intermediate transfer member;
and
a fixing step of heat-fixing the toner image transferred to the
transfer medium;
wherein said toner comprises toner particles containing at least a
binder resin, a colorant, a wax and a compound represented by
Formula (A): ##STR48## wherein R.sub.1 and R.sub.4 each represent a
substituted or unsubstituted aromatic group, inclusive of a
condensed ring; R.sub.2 and R.sub.3 each represent a hydrogen atom,
an alkyl group, a substituted or unsubstituted aromatic group,
inclusive of a condensed ring; M represents an element selected
from B, Ti, Fe, Co, Cr, Al and Ni; and X.sup.n+ represents a
cation, and said toner has shape factors SF-1 and SF-2 with a value
of 100<SF-1.ltoreq.160 and a value of
100<SF-2.ltoreq.140.
31. The image forming method according to claim 30, wherein, in
said developing step, the surface movement speed of the toner
carrying member at its developing zone is a speed of from 1.05 to
3.0 times the surface movement speed of the electrostatic latent
image bearing member.
32. The image forming method according to claim 30, wherein the
toner carrying member has a surface roughness Ra (.mu.m) of 1.5 or
less.
33. The image forming method according to claim 30, wherein, in
said developing step, the surface movement speed of the toner
carrying member at its developing zone is a speed of from 1.05 to
3.0 times the surface movement speed of the electrostatic latent
image bearing member, and the toner carrying member has a surface
roughness Ra (.mu.m) of 1.5 or less.
34. The image forming method according to claim 30, wherein a
ferromagnetic metal blade is provided opposingly to the toner
carrying member, leaving a minute gap between them.
35. The image forming method according to claim 30, wherein a blade
comprising an elastic material is brought into touch with the toner
carrying member.
36. The image forming method according to claim 30, wherein, in
said charging step, the charging member is brought into contact
with the electrostatic latent image bearing member to charge the
electrostatic latent image bearing member.
37. The image forming method according to claim 30, wherein, in
said transfer step, the electrostatic latent image bearing member
or intermediate transfer member comes into contact with a transfer
assembly with intervention of the transfer medium.
38. The image forming method according to claim 30, wherein said
fixing step comprises heat-fixing the toner image by means of a
heat-fixing assembly to which any offset-preventive liquid is not
fed or which do not have any fixing cleaner.
39. The image forming method according to claim 30, which has a
toner reuse mechanism in which transfer residual toner remaining on
the electrostatic latent image bearing member after said transfer
step is collected by cleaning and the toner collected is supplied
to a developing means to make the developing means again hold the
toner to develop the electrostatic latent image formed on the
electrostatic latent image bearing member.
40. The image forming method according to claim 30, wherein, in
said developing step, a toner layer formed of the toner carried on
the surface of the toner carrying member comes into contact with
the surface of the electrostatic latent image bearing member to
develop the electrostatic latent image.
41. The image forming method according to claim 40, wherein, in
said developing step, transfer residual toner remaining on the
electrostatic latent image bearing member after said transfer step
is collected at the time the electrostatic latent image is
developed.
42. The image forming method according to claim 30, wherein in said
toner the shape factor SF-1 is 100<SF-2.ltoreq.150 and the shape
factor SF-2 is 100<SF-2.ltoreq.130.
43. The image forming method according to claim 30, wherein in said
toner the shape factor SF-1 is 100<SF-1.ltoreq.140 and the shape
factor SF-2 is 100<SF-2.ltoreq.120.
44. The image forming method according to claim 30, wherein in said
toner the ratio of the shape factor SF-1 to the shape factor SF-2,
(SF-2)/(SF-1), is in a value of 1 or less.
45. The image forming method according to claim 30, wherein said
toner has an average circularity of from 0.920 to 0.995 and a
circularity standard deviation of less than 0.040 in its
circularity frequency distribution as measured with a flow type
particle image analyzer.
46. The image forming method according to claim 30, wherein said
toner has an average circularity of from 0.950 to 0.995 and a
circularity standard deviation of less than 0.040 in its
circularity frequency distribution as
measured with a flow type particle image analyzer.
47. The image forming method according to claim 30, wherein said
toner has an average circularity of from 0.970 to 0.990 and a
circularity standard deviation of from 0.015 to less than 0.035 in
its circularity frequency distribution as measured with a flow type
particle image analyzer.
48. The image forming method according to claim 30, wherein in said
toner a toner having an average circularity less than 0.950 in its
circularity frequency distribution is in a content of 15% by number
or less.
49. The image forming method according to claim 30, wherein said
toner has a weight-average particle diameter of from 4 .mu.m to 9
.mu.m.
50. The image forming method according to claim 30, wherein said
toner has a coefficient of variation in number distribution, of 30
or less.
51. The image forming method according to claim 30, wherein said
toner has a toner fine powder having particle diameters of 4.00
.mu.m or smaller in number distribution in a content not more than
25% by number.
52. The image forming method according to claim 30, wherein said
toner has a weight-average particle diameter of from 4 .mu.m to 9
.mu.m, has a coefficient of variation in number distribution, of 30
or less, and has a toner fine powder having particle diameters of
4.00 .mu.m or smaller in number distribution in a content not more
than 25% by number.
53. The image forming method according to claim 30, wherein said
toner has a weight-average particle diameter of from 4 .mu.m to 9
.mu.m, has a coefficient of variation in number distribution, of 25
or less, and has a toner fine powder having particle diameters of
4.00 .mu.m or smaller in number distribution in a content not more
than 20% by number.
54. The image forming method according to claim 30, wherein said
wax is dispersed in the form of substantially a spherical or
spindle-shaped island or islands in such a way that, when in
cross-sectional observation of toner particles on a transmission
electron microscope (TEM);
(1) twenty planes of cross sections of toner particles having
length R (.mu.m) satisfying the relation of
0.9.ltoreq.R/D4.ltoreq.1.1 with respect to weight-average particle
diameter D4 (.mu.m) are picked up; and
(2) each length r of the largest among phase-separated structures
ascribable to the wax present in the cross-sectional plane of the
toner particles thus picked up is measured;
the arithmetic mean value of r/R, (r/R).sub.st, thus determined
satisfies:
55. The image forming method according to claim 54, wherein the
(r/R).sub.st satisfies:
56. The image forming method according to claim 30, wherein said
wax has a maximum endothermic peak at from 50.degree. C. to
100.degree. C. at the time of temperature rise, in the DSC curve as
measured with a differential scanning calorimeter.
57. The image forming method according to claim 30, wherein said
wax is an ester wax having ester compounds satisfying the following
general formula.
wherein R.sub.1 and R.sub.2 each represent a hydrocarbon group
having 15 to 45 carbon atoms.
58. The image forming method according to claim 57, wherein said
ester wax contains ester compounds having the same number of carbon
atoms in total, in an amount of from 50% by weight to 95% by
weight.
59. The image forming method according to claim 30, wherein said
toner contains an inorganic fine powder.
60. The image forming method according to claim 59, wherein said
inorganic fine powder has been treated with silicone oil.
61. The image forming method according to claim 30, wherein said
toner is negatively chargeable.
62. The image forming method according to claim 30, wherein said
toner contains the compound represented by Formula (A) in an amount
of from 0.1 part by weight to 10 parts by weight based on 100 parts
by weight of the binder resin.
63. The image forming method according to claim 30, wherein said
toner contains the compound represented by Formula (A) in an amount
of from 0.6 part by weight to 5 parts by weight based on 100 parts
by weight of the polymerizable monomer.
64. The image forming method according to claim 30, wherein said
toner particles are obtained by subjecting a polymerizable monomer
composition containing a polymerizable monomer, the wax and the
compound represented by Formula (A), to suspension polymerization
in an aqueous medium.
65. The image forming method according to claim 64, wherein said
compound represented by Formula (A) is added in an amount of from
0.1 part by weight to 10 parts by weight based on 100 parts by
weight of the polymerizable monomer.
66. The image forming method according to claim 64, wherein the
compound represented by Formula (A) is added in an amount of from
0.6 part by weight to 5 parts by weight based on 100 parts by
weight of the polymerizable monomer.
Description
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a toner and an image forming method which
are used in recording processes such as electrophotography,
electrostatic recording, magnetic recording and toner-jet
recording. More particularly, the present invention relates to a
toner and an image forming method which are used in copying
machines, printers and facsimile machines in which toner images are
previously formed on an electrostatic latent image bearing member
and thereafter transferred onto transfer mediums to form images.
The present invention also provides a process for producing the
toner.
2. Related Background Art
A number of methods are known as electrophotography. In general,
final images are obtained by forming an electrostatic latent image
on a
photosensitive member by utilizing a photoconductive material and
by various means, subsequently developing the latent image by the
use of a toner to form a toner image as a visible image,
transferring the toner image to a transfer medium, and then fixing
to the transfer medium the toner image formed thereon, by heating
and/or pressing.
As methods by which the electrostatic latent image is formed into a
visible image, developing methods such as cascade development,
magnetic brush development and pressure development are known in
the art. Another method is also known in which, using a magnetic
toner and using a rotary sleeve provided with a magnet at the core,
the magnetic toner is caused to fly across the sleeve and a
photosensitive member by the aid of an electric field.
One-component development systems require no carrier such as glass
beads or iron powder required in two-component development systems,
and hence can make developing assemblies themselves small-sized and
light-weight. Also, since in the two-component development systems
the concentration of toner in carrier must be kept constant, a
device for detecting toner concentration so as to supply the toner
in the desired quantity is required, resulting in a large size and
weight for the developing assemblies. In the one-component
development system, such a device is not required, and hence the
developing assemblies can also be made small and light as being
preferable.
As printers, LED printers or LBP printers are prevailing in the
recent market. As a trend of techniques, there is a tendency toward
higher resolution. More specifically, those which hitherto have a
resolution of 300 or 600 dpi are being replaced by those having a
resolution of 1,200 or 2,400 dpi. accordingly, with such a trend,
the developing systems are now required to achieve a high
minuteness. Copying machines have also progressed to have higher
functions, and hence they trend toward digital systems. In this
trend, chiefly employed is a method in which electrostatic latent
images are formed by using a laser. Hence, the copying machines
also trend toward a high resolution and, like the printers, it has
been sought to provide a developing system with higher resolution
and higher minuteness.
Accordingly, in order to meet such a demand, a specific charge
control agent is added so that the desired triboelectric
chargeability can be imparted to toner particles. Charge control
agents nowadays known in the present technical field include, as
those for controlling negative triboelectric chargeability, metal
complex salts of monoazo dyes, metal complex salts of
hydroxycarboxylic acids, dicarboxylic acids and aromatic diols, and
resins containing acid components. As those for controlling
positive triboelectric chargeability, they are known to include
nigrosine dyes, azine dyes, triphenylmethane dyes, quaternary
ammonium salts, and polymers having quaternary ammonium salts in
the side chains.
Proposals have ever been made in regard to toners containing metal
compounds of oxycarboxylic acids. For example, Japanese Patent
Application Laid-Open No. 2-221967 discloses a toner containing a
metal complex salt of an oxycarboxylic acid having an aromatic
ring. Japanese Patent Application Laid-Open No. 5-61257 discloses a
toner comprising a toner precursor in which a boron compound of an
oxycarboxylic acid has been embedded. Japanese Patent Application
Laid-Open Nos. 3-39973 and 5-72812 discloses a toner containing a
boron complex salt of benzilic acid. Japanese Patent Application
Laid-Open No. 5-165257 discloses a color toner containing a boron
complex salt of benzilic acid and an inorganic fine powder
subjected to hydrophobic-treatment with silicone oil. Japanese
Patent Application Laid-Open No. 6-301240 discloses a color toner
containing a benzilic acid metal complex salt having an amide as a
counter ion. These toners were improved in their charging rate to a
certain extent. However, these have such disadvantages that a
sufficient quantity of triboelectricity cannot be imparted to the
toner.
In order to eliminate such a problem, Japanese Patent Application
Laid-Open No. 10-90946 discloses a toner comprising toner particles
in which a charge control agent such as a boron complex salt of
benzilic acid has been added and fixed without being dried.
Japanese Patent Application Laid-Open No. 10-312089 also discloses
a toner using a boron complex salt of benzilic acid and a metal
salt of a salicylic acid derivative in combination. According to
studies of the present inventors, these toner can achieve an
improvement in the quantity of triboelectricity and the charging
rate to a certain extent. However, in the former case a complicated
production process is required, and in the latter case the use of a
boron complex salt of benzilic acid and a metal salt of a salicylic
acid derivative in combination results in inclusion of charge
control agents presenting different triboelectric series. Thus,
there has been room for further improvement in regard to
triboelectric charge quantity distribution. Also, in the above
toners, further reseaches have been required for matching
themselves to image forming apparatus.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a toner and an
image forming method which have solved the problems the prior art
has had.
More specifically, an object of the present invention is to provide
a toner and an image forming method which are superior in transfer
performance and less in transfer residual toner.
Another object of the present invention is to provide a toner and
an image forming method which do not adversely affect the
photosensitive member or intermediate transfer member, may less
cause image deterioration such as fog and are highly applicable to
electrophotographic processes.
Still another object of the present invention is to provide a toner
and an image forming method which are used for an electrostatic
latent image bearing member having good releasability and slip
properties, retaining such functions over a long period of time and
less undergoing photosensitive member scrape even after printing
many sheets to enjoy a long service life.
A further object of the present invention is to provide a toner and
an image forming method which do not cause any abnormal charging or
faulty images due to contamination of a member coming into pressure
contact with an electrostatic latent image bearing member, or can
restrain such a phenomenon from occurring, and are well matchable
to image forming apparatus.
A still further object of the present invention is to provide a
toner and an image forming method in which the performance of
uniformly coating toner on a toner carrying member is enhanced.
To achieve the above objects, the present invention provides a
toner comprising toner particles containing at least a binder
resin, a wax and a compound represented by Formula (A);
the toner having shape factors SF-1 and SF-2 with a value of
100<SF-1.ltoreq.160 and a value of 100 <SF-2.ltoreq.140.
Formula (A) ##STR2## wherein R.sub.1 and R.sub.4 each represent a
substituted or unsubstituted aromatic group, inclusive of a
condensed ring; R.sub.2 and R.sub.3 each represent a hydrogen atom,
an alkyl group, a substituted or unsubstituted aromatic group,
inclusive of a condensed ring; M represents an element selected
from B, Ti, Fe, Co, Cr, Al and Ni; and X.sup.n+ represents a
cation.
The present invention also provides a process for producing a
toner, comprising;
a granulation step of dispersing in an aqueous medium a
polymerizable monomer composition containing at least a
polymerizable monomer, a colorant, a wax, a polymerization
initiator and a compound represented by Formula (A), to form
particles of the polymerizable monomer composition; and
a polymerization step of polymerizing the polymerizable monomer
present in the particles of the polymerizable monomer composition
to form toner particles;
the polymerization reaction of the polymerizable monomer from the
granulation step to the polymerization step being carried out while
keeping the pH of the aqueous medium at 4.5 to 8.5, until the
polymerization conversion of the polymerizable monomer comes to be
10% or more; and
the toner having shape factors SF-1 and SF-2 with a value of
100<SF-1.ltoreq.160 and a value of 100<SF-2.ltoreq.140.
Formula (A) ##STR3## wherein R.sub.1 and R.sub.4 each represent a
substituted or unsubstituted aromatic group, inclusive of a
condensed ring; R.sub.2 and R.sub.3 each represent a hydrogen atom,
an alkyl group, a substituted or unsubstituted aromatic group,
inclusive of a condensed ring; M represents an element selected
from B, Ti, Fe, Co, Cr, Al and Ni; and X.sup.n+ represents a
cation.
The present invention still also provides an image forming method
comprising;
a charging step of applying a voltage to a charging member from the
outside to charge an electrostatic latent image bearing member;
a latent image forming step of forming an electrostatic latent
image on the electrostatic latent image bearing member thus
charged;
a developing step of developing the electrostatic latent image by
the use of a toner to from a toner image on the electrostatic
latent image bearing member;
a transfer step of transferring the toner image formed on the
electrostatic latent image bearing member, to a transfer medium
with or without intervention of an intermediate transfer member;
and
a fixing step of heat-fixing the toner image transferred to the
transfer medium;
wherein the toner comprises toner particles containing at least a
binder resin, a wax and a compound represented by Formula (A); and
the toner has shape factors SF-1 and SF-2 with a value of
100<SF-1.ltoreq.160 and a value of 100<SF-2.ltoreq.140.
Formula (A) ##STR4## wherein R.sub.1 and R.sub.4 each represent a
substituted or unsubstituted aromatic group, inclusive of a
condensed ring; R.sub.2 and R.sub.3 each represent a hydrogen atom,
an alkyl group, a substituted or unsubstituted aromatic group,
inclusive of a condensed ring; M represents an element selected
from B, Ti, Fe, Co, Cr, Al and Ni; and X.sup.n+ represents a
cation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows an example of a gas chromatogram of an ester wax.
FIG. 2 is a schematic illustration of an image forming apparatus
suited for the present invention.
FIG. 3 is an enlarged transverse cross-sectional view of the main
part of a developing assembly for a two-component developer used in
Examples of the present invention.
FIG. 4 is an enlarged transverse cross-sectional view of the main
part of a developing assembly for a one-component developer used in
Examples of the present invention.
FIG. 5 is an exploded perspective view of the main part of a fixing
assembly used in Examples of the present invention.
FIG. 6 is an enlarged transverse cross-sectional view of the main
part showing how a film stands when a fixing assembly used in
Examples of the present invention is not driven.
FIG. 7 is a diagrammatic illustration of an image forming method
employing a contact one-component developing assembly, used in
Examples as an examples of the image forming method of the present
invention.
FIG. 8 is a diagrammatic illustration of an image forming method
employing a contact one-component developing assembly, used as
another example of the image forming method of the present
invention.
FIG. 9 is an enlarged cross-sectional view of a developing assembly
of the image forming apparatus shown in FIGS. 7 and 8.
FIG. 10 is a schematic illustration of an image forming apparatus
which reuses untransferred toner.
FIGS. 11A and 11B are diagrammatic illustrations of cross sections
of toner particles in which a wax is embraced.
FIG. 12 is a perspective view of a device for measuring the
quantity of triboelectricity of toners, used in the present
invention.
FIGS. 13A and 13B diagrammatically illustrate the state of blank
areas caused in character images.
FIG. 14 illustrates an isolated-dot pattern used to evaluate dot
reproducibility.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The toner of the present invention contains at least a binder
resin, a wax and, as a charge control agent, a compound represented
by Formula (A).
The compound represented by Formula (A) will be described below in
detail.
Formula (A) ##STR5##
In the formula, R.sub.1 and R.sub.4 each represent a substituted or
unsubstituted aromatic group, inclusive of a condensed ring;
R.sub.2 and R.sub.3 each represent a hydrogen atom, an alkyl group,
a substituted or unsubstituted aromatic group, inclusive of a
condensed ring; M represents an element selected from B, Ti, Fe,
Co, Cr, Al and Ni; and X.sup.n+ represents a cation.
Stated specifically, the aromatic groups represented by R.sub.1,
R.sub.2, R.sub.3 and R.sub.4 may include benzene and naphthalene.
The substituents of the aromatic groups may include an alkyl group,
an aralkyl group, an alkoxyl group, an alkenyl group, an aryl
group, a halogen atom, a nitro group, a cyano group, an amino group
and a hydroxyl group. The alkyl groups represented by R.sub.2 and
R.sub.3 may include a methyl group, an ethyl group, a n-butyl
group, a t-butyl group, an isopropyl group, an isoamyl group, a
n-dodecyl group, a n-octadecyl group and a cyclohexyl group. The
element represented by M may preferably include trivalent metals
Cr, Al, Fe, Co, Ti and B. As the X.sup.n+, various inorganic
cations and organic cations may be used. The inorganic cations may
include hydrogen ions and metal ions, and the metal ions may
include monovalent or divalent metal ions such as Li.sup.+,
Na.sup.+, Mg.sup.2+, Ca.sup.2+, Zn.sup.2+ and Ba.sup.2+. The
organic cations may include ammonium ions, iminium ions and
phosphonium ions.
Of the cations X.sup.n+ exemplified above, inorganic cations are
preferred in view of charging rate and charging stability.
Of the above organic cations, preferred are those represented by
the following Formulas (B), (C), (D) and (E). ##STR6##
In the formulas, R.sub.5 to R.sub.15 each represent a hydrogen
atom, a substituted or unsubstituted alkyl group or a substituted
or unsubstituted aryl group, and Z.sub.1 and Z.sub.2 in Formulas
(B), (C) and (D) each represent a non-metallic atomic group which
combines with the nitrogen atom of the cation of each Formula to
form a 5-membered ring or a 6-membered ring.
The alkyl group may include a methyl group, an ethyl group, an
n-butyl group, a t-butyl group, an isopropyl group, an isoamyl
group, an n-dodecyl group, an n-octadecyl group and a cyclohexyl
group. The aryl group may include a phenyl group and an a-naphthyl
group, and these alkyl groups may be substituted with a substituent
such as an alkyl group, an aralkyl group, a halogen atom, an
alkoxyl group, a hydroxyl group, a cyano group or an aryl group.
The groups Z.sub.1 and Z.sub.2 may include non-metallic atomic
groups necessary to form heterocyclic rings such as a pyridine
ring, an isoquinoline ring, a pyrrole ring, an imidazole ring, a
piperidine ring and a pyrrolidine ring.
Examples of the compound represented by Formula (A) are shown in
Tables 1 and 2 below. In the following, the compound number (No.)
is also used in common in Examples.
The compound represented by Formula (A), which is used as a charge
control agent in the present invention, is readily obtained by,
e.g., adding a compound represented by Formula (F) or (G) [wherein
R.sub.1 to R.sub.4 are as defined in Formula (A)] in an aqueous
solution of boric acid and an amine to carry out reaction.
##STR7##
When the toner is produced by polymerization, the compound
represented by Formula (A) may be added in an amount of from 0.1 to
10 parts by weight, and preferably from 0.6 to 5 parts by weight,
based on 100 parts by weight of the polymerizable monomer.
The compound represented by Formula (A), added in the toner
components may usually be in an amount of from 0.1 to 10 parts by
weight, and preferably from 0.6 to 5 parts by weight, based on 100
parts by weight of the polymerizable monomer.
Addition of the Formula (A) compound in the toner components in an
amount less than 0.1 part by weight is not preferable because the
effect of charging toner particles can not be obtained. Addition of
the Formula (A) compound in an amount more than 10 parts by weight
results in a high cost and is not preferable from an economical
viewpoint.
The toner of the present invention has specific shape factors SF-1
and SF-2.
In the present invention, the SF-1 and SF-2 each indicating the
shape coefficient of the toner are values obtained by sampling at
random 100 images of 2 .mu.m or larger toner particle as magnified
1,000 times with, e.g., FE-SEM (S-800; a scanning electron
microscope manufactured by Hitachi Ltd.), introducing their image
information into an image analyzer (e.g., LUSEX III; manufactured
by Nikore Co.) through an interface to make analysis, and
calculating the data according to the following expression. The
values thus obtained are defined as shape coefficient SF-1,
SF-2.
wherein MXLNG represents an absolute maximum length of a particle;
PERIME represents a peripheral length of the particle; and AREA
represents a projected area of the particle.
When the shape factors of toner particles are measured by the above
method after any external additive has been added to the toner
particles, they are so measured that the external additive having
adhered to the toner particle surfaces are not included in the data
for image analysis.
The shape factor SF-1 of toner indicates the degree of sphericity
of a particle, and the shape factor SF-2 indicates the degree of
unevenness of the particle.
If the shape factor ratio of the toner SF-2)/(SF-1) is in a value
more than 1.0, faulty leaning tends to occur in usual instances. If
the shape factor SF-1 is more than 160, the particle becomes less
spherical, and more amorphous (shapeless), so that the toner
particles tend to be pulverized in the developing assembly and to
cause variations of particle size distribution or result in a broad
charge quantity distribution. A shape factor SF-2 of more than 140
is not preferable because the toner image may be transferred in a
low transfer efficiency when transferred from the photosensitive
member to the intermediate transfer member and also to the transfer
medium and blank areas may be caused by poor transfer in character
or line images.
The tendencies as stated above may be remarkable especially when a
full-color copying machine in which a plurality of toner images are
developed and transferred is used. More specifically, when a
full-color image is formed, the four color toner images are hard to
uniformly transfer, and also, when the intermediate transfer member
is used, a problem is liable to occur in respect of color
uniformity and color balance, and it is hard to stably reproduce
high-quality full-color images.
In addition, when a usual amorphous toner is used, melt-adhesion or
filming of toner may occur on the photosensitive member surface or
intermediate transfer ember surface because of a shear force or
rubbing force acting between the photosensitive member and the
cleaning member and/or between the photosensitive member and the
intermediate transfer member.
Accordingly, in order to avoid these problems, the toner of the
present invention may preferably have shape factors SF-1 and SF-2
with a value of 100<SF-1.ltoreq.160 and a value of
100<SF-2.ltoreq.140, more preferably shape factors SF-1 and SF-2
with a value of 100<SF-1.ltoreq.150 and a value of
100<SF-2.ltoreq.130, and still more preferably shape factors
SF-1 and SF-2 with a value of 100<SF-1.ltoreq.140 and a value of
100<SF-1.ltoreq.120. Also, the value of (SF-2)/(SF-1) may
preferably be 1.0 or less.
The toner of the present invention can be prevented from
melt-adhering to the toner carrying member due to an increase in
transfer residual toner or a lowering of developing efficiency,
especially when a toner having a good circularity distribution is
produced.
In the toner of the present invention, the particle shape of the
toner may precisely be so controlled that the toner can have an
average circularity of from 0.920 to 0.995 and a circularity
standard deviation of less than 0.040 in circularity frequency
distribution of the toner as measured with a low type particle
image analyzer, whereby the toner an be improved in developing
performance and transfer performance in a well balanced state and
also can greatly be improved so as to match itself to image forming
apparatus.
More specifically, when the toner is made to have an average
circularity of from 0.920 to 0.995, preferably from 0.950 to 0.995,
and more preferably from 0.970 to 0.990 in its circularity
frequency distribution, the toner having a small particle diameter
can greatly be improved in transfer performance, which has ever
been difficult to do, and also can greatly be improved in the
developability for low-potential latent images. Such tendencies are
very effectively appear especially when a digital system of minute
spot latent images are developed or when toner images are
transferred many times through the intermediate transfer member to
form a full-color image, bringing about a good compatibility with
image forming apparatus.
In the toner of the present invention, it is also possible to
arbitrarily control the circularity standard deviation of
circularity frequency distribution of the toner. The circularity
standard deviation may be controlled to be less than 0.040,
preferably less than 0.035, and more preferably from 0.015 to less
than 0.035. This can bring about a great improvement in properties
relating to developing performance.
A toner having an average circularity less than 0.950 in its
circularity frequency distribution may be in a content of 15% by
number or less. This brings the development efficiency in image
formation to a satisfactory level and also enables good images to
be formed.
The average circularity, the circularity standard deviation and the
percent by number of the toner having an average circularity less
than 0.950 can be controlled by adjusting the pH of an aqueous
medium in the step of granulation in suspension polymerization.
The circularity and the frequency distribution thereof referred to
in the present invention are used as a simple method for expressing
the shape of toner quantitatively. In the present invention, they
are measured with a flow type particle image analyzer FPIA-1000,
manufactured by Toa Iyou Denshi K.K., and the average circularity
is calculated according to the following expression.
Circularity= ##EQU1##
Here, the "particle projected area" is meant to be the area of a
binary-coded toner particle image, and the "circumferential length
of particle projected image" is defined to be the length of a
contour line formed by connecting edge points of the toner particle
image.
The circularity referred to in the present invention is an index
showing the degree of surface unevenness of toner particles. It is
indicated as 1.000 when the toner particles are perfectly
spherical. The more complicate the surface shape is, the smaller
the value of circularity is.
Average circularity c which means an average value of circularity
frequency distribution and circularity distribution SDc are
calculated from the following expression where the circularity at a
partition point i of particle size distribution (a central value)
is represented by ci, and the frequency by f.sub.ci.
As a specific measuring method, 10 ml of ion-exchanged water from
which impurity solid matter has been removed is put in a container,
and as a dispersant a surface-active agent, preferably alkylbenzene
sulfonate, is added therein. Thereafter, 0.02 g of a sample to be
measured is further added therein, then uniformly dispersed. As a
dispersing means, an ultrasonic dispersion machine UH-50
(manufactured by SMT Co.) to which a 5 mm diameter titanium alloy
tip is attached as a vibrator is used, and dispersion treatment is
carried out for 5 minutes to prepare a dispersion for measurement.
Here, the dispersion is appropriately cooled so that its
temperature does not exceed 40.degree. C.
The toner shape is measured using the above flow type particle
image analyzer. Concentration of the dispersion is again so
adjusted that the toner particles are in a concentration of from
3,000 to 10,000 particles/.mu.l at the time of measurement, and
1,000 or more particles are measured. After measurement, the data
obtained are used to determine a circle-corresponding diameter and
circularity frequency distribution of the toner.
In order to faithfully develop minute latent image dots to make
image quality higher, the toner may preferably have a
weight-average particle diameter (D4) of from 4 to 9 .mu.m and a
coefficient of variation A in number distribution, of 30t or less,
and may more preferably have a coefficient of variation A of 25 or
less. Also, a toner fine powder having particle diameters of 4.00
.mu.m or smaller in number distribution may preferably be in a
content not more than 25% by number, and more preferably not more
than 20% by number. Controlling toner particle size distribution in
such a manner as described above allows the toner particles to have
good powder characteristics. Accordingly, when the compound
represented by Formula (A) according to the present invention is
added and used in the toner, a very good charging performance can
be exhibited. If the toner has a weight-average particle diameter
smaller than 4 .mu.m or the toner fine powder is in a content more
than 25% by number, its fluidity may lower when toner particles are
loaded, and hence it tends to become difficult for the toner to be
triboelectrically charged uniformly, causing uneven image density
or image fog, or a decrease in image density. Transfer efficiency
may also lower, and hence this not only can be a cause of uneven
image density, but also may result in an increase in transfer
residual toner on the surface of the photosensitive member or
intermediate transfer member, undesirably resulting in an increase
in a load on the image forming apparatus.
If on the other hand the toner has a weight-average particle
diameter larger than 10 .mu.m, the minute latent image dots may no
longer faithfully be reproduced.
In the past, the use of toner particles having such a small
particle diameter have often caused problems concerning the
charging performance of toners. However, when the compound
represented by Formula (A) according to the present invention is
added in the toner, the toner can be more improved in uniform
charging performance and charging stability.
The particle size distribution of the toner may be measured by
various methods. In the present invention, it is measured with a
Coulter counter Model TA-II or Coulter Multisizer (both
manufactured by Coulter Electronics, Inc.) as a measuring device.
As an electrolytic solution for measurement, an aqueous 1% by
weight NaCl solution of first-grade sodium chloride is prepared and
used, or commercially available ISOTON R-II (trade name,
manufactured by Coulter Scientific Japan Co.) may be used.
Measurement is carried out by adding as a dispersant 0.1 to 5 ml of
a surface active agent, preferably an alkylbenzene sulfonate, to
100 to 150 ml of the above electrolytic solution, and further
adding 2 to 20 mg of a sample to be measured. Next, the
electrolytic solution to which the measuring sample has been added
is subjected to dispersion for about 1 minute to about 3 minutes in
an ultrasonic dispersion machine. Using an aperture of 100 .mu.m in
the above particle size distribution measuring device, the volume
and number of toner particles are measured for each channel, and
the volume distribution and number distribution of the toner are
calculated, and the weight-average particle diameter (D4) of the
toner is determined from that volume distribution, and the
number-average particle diameter (D1) and standard deviation (S)
from that number distribution.
As measuring channels, the following 13 channels are set: 2.00 to
less than 2.52 .mu.m, 2.52 to less than 3.17 .mu.m, 3.17 to less
than 4.00 .mu.m, 4.00 to less than 5.04 .mu.m, 5.04 to less than
6.35 .mu.m, 6.35 to less than 8.00 .mu.m, 8.00 to less than 10.08
.mu.m, 10.08 to less than 12.70 .mu.m, 12.70 to less than 16.00
.mu.m, 16.00 to less than 20.20 .mu.m, 20.20 to less than 25.40
.mu.m, 25.40 to less than 32.00 .mu.m, and 32.00 to less than 40.30
.mu.m. The middle value of each channel is used as the
representative value of each channel for calculating the particle
size distribution.
The coefficient of variation A of number distribution of the toner
is calculated according to the following expression.
wherein S represents a value of standard deviation in the number
distribution of toner particles, and D1 represents number-average
particle diameter (.mu.m) of the toner particles.
The binder resin used in the toner according to the present
invention may preferably have a low-molecular weight peak ranging
from 3,000 to 150,000 in GPC molecular weight so that the shape of
toner particles produced by pulverization can be controlled by
thermomechanical impact force.
If the binder resin has a low-molecular weight peak at more than
150,000, it may be difficult to control the shape factors SF-1 and
SF-2 within the range of the present invention, resulting in
insufficient improvement of transfer efficiency. If the peak is at
less than 3,000, melt-adhesion tends to occur.
Molecular weight is measured by GPC (gel permeation
chromatography). As a specific method for measurement by GPC, a
sample obtained by beforehand subjecting the toner to extraction
with a THF (tetrahydrofuran) solvent for 20 hours by means of a
Soxhlet extractor. As column constitution, A-801, A-802, A-803,
A-804, A-805, A-806 and A-807, available from Showa Denko K.K., are
connected, and the molecular weight distribution is measured using
a calibration curve of standard polystyrene resin.
The binder resin used in the toner according to the present
invention may preferably have a ratio of weight-average molecular
weight (Mw) to number-average molecular weight (Mn), Mw/Mn, of from
2 to 100.
The binder resin used in the toner may preferably have a glass
transition point Tg of from 40.degree. C. to 75.degree. C., and
more preferably from 52.degree. C. to 70.degree. C., in view of
fixing performance and storage stability.
The glass transition point Tg of the binder resin used in the toner
according to the present invention is measured by, e.g., using a
differential scanning calorimeter of a highly precise, inner-heat
input compensation type, such as DSC-7, manufactured by Perkin
Elmer Co. It is measured according to ASTM D3418-82. The
temperature of a sample is once raised to take a previous history
and thereafter dropped rapidly. Then, the temperature is again
raised at a temperature rise rate of 10.degree. C./min within the
temperature range of 0 to 200.degree. C. The DSC curve thus
measured is used in the present invention.
In general, in the toner having the particle size distribution as
previously described, the state of charging is uniformed as the
particle
shape is uniformed, but the quantity of triboelectricity tends to
decrease with a decrease in surface area. Since, however, the toner
of the present invention contains the compound represented by
Formula (A), the changed state of the toner can be improved without
lowering the quantity of triboelectricity.
The binder resin used in the present invention may be any of those
used in the production of toners and there are no particular
limitations. As examples of the binder resin used in the present
invention, named are homopolymers of polymerizable monomers shown
below, or mixtures of homopolymers of the polymerizable monomers,
or copolymers of two or more of the polymerizable monomers. Stated
more specifically, styrene-acrylic acid type copolymers or
styrene-methacrylic acid type copolymers are preferred.
Styrene type polymerizable monomers may include, e.g., styrene, and
styrene derivatives such as o-methylstyrene, m-methylstyrene,
p-methylstyrene, p-methoxystyrene, p-phenylstyrene,
p-chlorostyrene, 3,4-dichlorostyrene, p-ethylstyrenee,
2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene,
p-n-hexystyelene, p-n-octylstyrene, p-n-nonylstyrene,
p-n-decylstyrene and p-n-dodecylstyrene.
Acrylate type polymerizable monomers may include, e.g., acrylic
esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate,
isobutyl acrylate, propyl acrylate, n-octyl acrylate, dodecyl
acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl
acrylate and phenyl acrylate. Methacrylate type polymerizable
monomers may include, e.g., .alpha.-methylene aliphatic
monocarboxylic esters such as methyl methacrylate, ethyl
methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl
methacrylate, n-octyl methacrylate, dodecyl methacrylate,
2-ethylhexyl methacrylate, stearyl methacrylate, phenyl
methacrylate, dimethylaminoethyl methacrylate and diethylaminoethyl
methacrylate.
In order to adjust fixing temperature of the toner, the binder
resin used in the present invention may preferably contain a
cross-linkable polymerizable monomer as exemplified below.
As the cross-linkable polymerizable monomer, a polymerizable
monomer having at least two polymerizable double bonds may be used.
Specific examples include aromatic divinyl compounds as exemplified
by divinylbenzene and divinylnaphthalene; diacrylate compounds
linked with an alkyl chain, as exemplified by ethylene glycol
diacrylate, 1,3-butylene glycol diacrylate, 1,4-butanediol
diacrylate, 1,5-pentanediol diacrylate, 1,6-hexanediol diacrylate,
neopentyl glycol diacrylate, and the above compounds whose acrylate
moiety has been replaced with methacrylate; diacrylate compounds
linked with an alkyl chain containing an ether linkage, as
exemplified by diethylene glycol diacrylate, triethylene glycol
diacrylate, tetraethylene glycol diacrylate, polyethylene glycol
#400 diacrylate, polyethylene glycol #600 diacrylate, dipropylene
glycol diacrylate, and the above compounds whose acrylate moiety
has been replaced with methacrylate; diacrylate compounds linked
with a chain containing an aromatic group and an ether linkage, as
exemplified by polyoxyethylene(2)-2,2-bis(4-hydroxyphenyl)propane
diacrylate, polyoxyethylene(4)-2,2-bis(4-hydroxyphenyl)propane
diacrylate, and the above compounds whose acrylate moiety has been
replaced with methacrylate; and also polyester type diacrylate
compounds as exemplified by MANDA (trade name; available from
Nippon Kayaku Co., Ltd.). Polyfunctional cross-linking agents may
include pentaerythritol triacrylate, trimethylolethane triacrylate,
trimethylolpropane triacrylate, tetramethylolpropane triacrylate,
tetramethylolmethane tetraacrylate, oligoester acrylate, and the
above compounds whose acrylate moiety has been replaced with
methacrylate; triallylcyanurate, and triallyltrimellitate.
Any of these cross-linkable polymerizable monomers may preferably
be used in an amount of 1 part by weight or less based on 100 parts
by weight of other polymerizable monomer components, whereby not
only low-temperature fixing performance and anti-offset properties
can well be satisfied but also the storage stability of toner can
be improved.
Of these cross-linkable polymerizable monomers, preferred is the
use of aromatic divinyl compounds (in particular, divinylbenzene)
and diacrylate compounds linked with a chain containing an aromatic
group and an ether linkage, any of which may be used in an amount
ranging from 0.001 to 0.05 part by weight based on 100 parts by
weight of other polymerizable monomer components. Thus, even when
toner particle diameter is made finer, developers can have a stable
developing performance in any environment, and also can be improved
in running performance.
To obtain the binder resin used in the present invention, it is
preferable to use a polymerization initiator as exemplified
below.
Stated specifically, usable are organic peroxides such as
di-t-butyl peroxide, dicumyl peroxide, benzoyl peroxide,
t-butylperoxy-2-ethylhexanoate and t-butylperoxybenzoate; and azo
and diazo compounds such as azobisbutyronitrile,
diazoaminoazobenzene, 2,2'-azobis-2-methylbutyronitrile,
2,2'-azobis(2-amidinobutane) dihydrochloride,
2,2'-azobis(2,4-dimethylvaleronitrile), and
dimethyl-2,2'-azobis(2-methylpropylate)(dimethyl-2,2'-a
zobisisobutyrate).
Any of these polymerization initiators may be used alone or in
combination, and may be used in an amount of from 0.05 to 20 parts
by weight, and more preferably from 0.5 to 10 parts by weight,
based on 100 parts by weight of the polymerizable monomers.
In the present invention, the binder resin described above may be
used in combination with a resin having a polarity (hereinafter
"polar resin") such as polyester resin or polycarbonate resin. The
addition of a polar resin in the toner brings about an improves a
state of the compound of Formula (A) contained in the toner, and
the charging performance can be improved.
For example, when the toner is directly produced by suspension
polymerization described later, such a polar resin may be added
during polymerization reaction from a dispersion step to a
polymerization step, thus, the formation of toner particles can be
so controlled that the polar resin added forms thin layers on the
surfaces of toner particles or is present in the toner particles
with a gradation from their surfaces to cores, in accordance with a
balance of the polarity shown by a toner particle-forming
polymerizable monomer composition and an aqueous dispersion medium.
Here, a polar resin that may interact with the compound represented
by Formula (A) may be used, whereby a state of the compound present
in the toner can be made into a desirable form. In particular, the
presence state of the compound can be easily controlled when a
polar resin having an acid value of from 1 to 20 mg KOH/g is
used.
The polar resin may preferably be used in an amount of from 1 to 25
parts by weight, and more preferably from 2 to 15 parts by weight,
based on 100 parts by weight of the binder resin. When used in an
amount less than 1 part by weight, the presence state of the polar
resin in the toner may be non-uniform, and when used in an amount
more than 25 parts by weight, the thin layers of polar resin formed
on the toner particle surfaces may be thicker. Hence, in both
instances, it may be difficult to control the presence state of the
compound represented by Formula (A), so that the polar resin can
not sufficiently exhibit its function.
A typical polyester resin used as the polar resin has the following
composition.
An alcohol component of the polyester resin may include ethylene
glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol,
2,3-butanediol, diethylene glycol, triethylene glycol,
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol,
2-ethyl-1,3-hexanediol, hydrogenated bisphenol A, a bisphenol
derivative represented by the following Formula (a) and a diol
represented by the following Formula (b): ##STR8## wherein R
represents an ethylene group or a propylene group, x and y are each
an integer of 1 or more, and an average value of x+y is 2 to 10;
##STR9## wherein R' represents ##STR10##
It is a preferred embodiment of the present invention to use a
reactive polyester resin or a polycarbonate resin as the polar
resin. When such a polar resin is used, the toner can be improved
in charging performance, the image fog and spots around line images
can be better prevented, and also high-grade images having superior
dot reproducibility can be formed. Also, it is possible to impart
an appropriate mechanical strength to the toner particles, so that
any influence of toner deterioration ascribable to image forming
apparatus can be confined to a minimum, bringing about improvements
in running performance against printing on a large number of sheets
and in the matching to image forming apparatus, as detailed later.
Moreover, when the toner particles are treated to be more spherical
so that the shape distribution of the toner as described previously
can be achieved or when the toner is directly produced by
suspension polymerization, any influence from toner production
steps such as drying can be confined to a minimum. Also, the polar
resin may be used in a combination of two or more kinds, and the
chargeability inherent in themselves can be utilized.
The reactive polyester resin used in the present invention includes
condensation polymers having a reactive group in the backbone or
side chain, which can be obtained by condensation polymerization of
a polybasic acid with a polyhydric alcohol; the polybasic acid
including terephthalic acid, isophthalic acid, adipic acid, maleic
acid, succinic acid, sebacic acid, thiodiglycolic acid, diglycolic
acid, malonic acid, glutaric acid, pimelic acid, suberic acid,
azelaic acid, comphoric acid, cyclohexanedicarboxylic acid and
trimellitic acid; and the polyhydric alcohol including ethylene
glycol, diethylene glycol, triethylene glycol, 1,2-propylene
glycol, 1,3-propylene glycol, 1,4-butane diol, neopentyl glycol,
1,4-bis(hydroxymethyl)cyclohexane, 1,4-bis(2-hydroxyethyl)benzene,
1,4-cyclohexanedimethanol, polyethylene glycol, polypropylene
glycol, bisphenol A, hydrogenated bisphenol, an ethylene oxide
addition product of bisphenol A, a propylene oxide addition product
of bisphenol A, glycerol, trimethylolpropane and pentaerythritol.
The reactive group may be exemplified by carboxylic acid (or a salt
thereof), sulfonic acid (or a salt thereof), ethyleneimino acid, an
epoxy group, an isocyanate group, a double bond, an acid anhydride
and a halogen atom. This reactive polyester resin may be allowed to
react with each other, or react with a polyfunctional cross-linking
agent (e.g., polyhydric alcohols and polybasic acids), or the
reactive polyester resin may further be allowed to react with a
vinyl monomer (e.g., esterification or copolymerization) to obtain
THF-insoluble matter. For example, when the toner is obtained by
polymerization, an unsaturated polyester resin may be used as the
reactive polyester, and copolymerized with the vinyl monomer
(optionally inclusive of a cross-linking agent such as
divinylbenzene). In such a case, the unsaturated polyester resin
having a polarity migrates to the vicinity of toner particle
surfaces with progress of polymerization to form thin layers on the
toner particle surfaces. Thus, it is possible to obtain a toner
having especially superior blocking resistance and anti-offset
properties.
In the present invention, any resin may be used as the reactive
polyester resin so long as it contain one of the reactive groups as
described above. However, when having a too low molecular weight,
polyester resins not involved in the cross-linking reaction may
consequently be present on the toner particle surfaces to cause a
lowering of blocking resistance in some cases. On the other hand,
when having a too high molecular weight, the reactive polyester
resin may be hard to dissolve in the vinyl monomer if the toner is
obtained in polymerization method, making the production of toner
difficult. Accordingly, the reactive polyester resin may preferably
have a weight-average molecular weight of from about 3,000 to about
100,000 in order to obtain a toner having especially superior
performances.
As for the polycarbonate resin used the present invention, a
polycarbonate resin having in its molecular structure a repeating
unit represented by the following Formula (I) may preferably be
used. ##STR11## wherein R represents an organic group.
The repeating unit represented by the above Formula (I) includes
those having various structures. All known polycarbonates produced
by, e.g., allowing divalent phenols to react with carbonate
precursors by a solution process or a melting process. For example,
it may include polymers having a repeating unit represented by the
following Formula (II) ##STR12## wherein R.sub.2 represents a
hydrogen atom, an aliphatic hydrocarbon group or an aromatic
substituent, m represents an integer of 0 to 4, and when R.sub.2 is
in plurality, they may be the same or different; and Z represents a
linkage represented by a single bond, an aliphatic hydrocarbon
group, an aromatic substituent, or --S--, --SO--, --SO.sub.2 --,
--O-- or --CO--linkage.
This polycarbonate resin is available from various routes. Usually,
it can readily be produced by allowing a divalent phenol
represented by any of Formulas (III) to (V): ##STR13## wherein
R.sub.2, m and Z are as defined above; to react with a carbonate
precursor such as phosgene or a carbonate compound. More
specifically, it can be produced by, e.g., allowing the divalent
phenol to react with a carbonate precursor such as phosgene or
subjecting the divalent phenol and a carbonate precursor such as
diphenyl carbonate to transesterification, in a solvent such as
methylene chloride in the presence of a known acid acceptor or
molecular weight modifier.
The divalent phenols represented by the above Formulas (III) to (V)
may include various ones, for example,
2,2-bis(4-hydroxyphenyl)propane (commonly called "bisphenol A"),
dihydroxyarylalkanes such as bis(4-hydroxyphenyl)methane,
bis(4-hydroxyphenyl)phenylmethane,
bis(4-hydroxyphenyl)naphthylmethane,
bis(4-hydroxyphenyl)-(4-isopropylphenyl)methane,
bis(3,5-dimethyl-4-hydroxyphenyl)methane,
1,1-bis(4-hydroxyphenyl)ethane,
1-naphthyl-1,1-bis(4-hydroxyphenyl)ethane,
1-phenyl-1,1-bis(4-hydroxyphenyl)ethane,
1,2-bis(4-hydroxyphenyl)ethane,
2-methyl-1,1-bis(4-hydroxyphenyl)propane,
2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane,
1-ethyl-1,1-bis(4-hydroxyphenyl)propane,
2,2-bis(3-methyl-4-hydroxyphenyl)propane,
1,1-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)butane,
1,4-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane,
4-methyl-2,2-bis(4-hydroxyphenyl )pentane,
1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(4-hydroxyphenyl
)hexane, 4,4-bis(4-hydroxyphenyl)heptane, 2,2-bis(4-hydroxyphenyl
)nonane, 1,10-bis(4-hydroxyphenyl)decane and
1,1-bis(4-hydroxyphenyl)cyclodecane; dihydroxyarylsulfones such as
bis(4-hydroxyphenyl)sulfone and
bis(3,5-dimethyl-4-hydroxyphenyl)sulfone; dihydroxyaryl ethers such
as bis(4-hydroxyphenyl) ether and bis(3,5-dimethyl-4-hydroxyphenyl)
ether; dihydroxyaryl ketones such as 4,4'-dihydroxybenzophenone and
3,3',5,5'-tetramethyl-4,4'-dihydroxybenzophenone; dihydroxyaryl
sulfides such as bis(4-hydroxyphenyl) sulfide,
bis(3-methyl-4-hydroxyphenyl) sulfide and
bis(3,5-dimethyl-4-hydroxyphenyl) sulfide; dihydroxyaryl sulfoxides
such as bis(4-hydroxyphenyl) sulfoxide; dihyroxydiphenyls such as
4,4'-dihydroxydiphenyl; dihyroxybenzenes such as hydroquinone,
resorcinol and methylhydroquinone; and dihyroxynaphthalenes such as
1,5-dihydroxynaphthalene and 2,6-dihydroxynaphthalene. These
divalent phenols may be used alone or in combination.
The carbonate compound may include diaryl carbonates such as
diphenyl carbonate, and dialkyl carbonates such as dimethyl
carbonate and diethyl carbonate.
The polycarbonate resin used in the present invention may be used
in the form of a homopolymer making use of one of these divalent
phenols, a copolymer making use of two or more of them, or a blend
of any of these.
It may also be a thermoplastic random-branched polycarbonate resin
obtained by allowing a polyfunctional aromatic compound to react
with the above divalent phenol and/or carbonate precursor.
In order to control the glass transition temperature or
viscoelasticity of the polycarbonate resin, a modified
polycarbonate resin may also preferably be used which has such a
form that part of the above divalent phenol has been substituted
with a polyhydric alcohol such as ethylene glycol, diethylene
glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene
glycol, 1,4-butanediol, neopentyl glycol,
1,4-bis(hydroxymethyl)cyclohexane, 1,4-bis(2-hydroxyethyl)benzene,
1,4-cyclohexanedimethanol, polyethylene glycol, propylene glycol,
hydrogenated bisphenol A or a derivative thereof, an ethylene oxide
addition product of bisphenol A, a propylene oxide addition product
of bisphenol A, glycerol, trimethylolpropane or pentaerythritol. In
this instance, it may be produced by simply substituting part of
the divalent phenol and by the above process. As another example of
the production process, a method may be used in which the divalent
phenol is reacted with an aliphatic or aromatic bischloroformate in
a methylene chloride solvent using pyridine as a catalyst. Of
course, it may be synthesized by any production process other than
these.
In the present invention, as the polycarbonate resin, it is also
possible to use a block copolymer of the above polycarbonate with a
polymer such as polystyrene, styrene-acrylic or methacrylic
copolymer, polyester, polyurethane, epoxy resin, polyolefin,
polyamide, polysulfone, polycyanoaryl ether or polyarylene sulfide,
and a graft-modified copolymer obtained by grafting an alkyl
acrylate or methacrylate monomer, an acrylic or methacrylic acid
monomer, a maleic acid monomer or a styrene monomer.
There are no particular limitations on the molecular weight of the
polycarbonate resin used in the present invention. The
polycarbonate resin may preferably be those having a peak molecular
weight within the range of from 1,000 to 500,000, and more
preferably from 2,000 to 100,000, as measured by GPC. If the peak
molecular weight is lower than 1,000, the resin may adversely
affect the charging performance, and if it is higher than 500,000,
the resin may have so high a melt viscosity as to cause a problem
in fixing performance in some cases. Also, when the polycarbonate
resin used in the present invention is produced, an appropriate
molecular weight modifier, a branching agent for improving
viscoelasticity, a catalyst for accelerating reaction and so forth
may be used as occasion calls.
The polar resin as described above is by no means limited to one
type of polymer for each case. For example, two or more types of
reactive polyester resins may simultaneously be used, or two or
more types of vinyl monomers may be used. Polymers of quite
different types may also optionally be added to the binder resin,
as exemplified by polymers such as polyester resins having no
reactivity, epoxy resins, polycarbonate resins, polyolefins,
polyvinyl acetate, polyvinyl chloride, polyalkyl vinyl ethers,
polyalkyl vinyl ketones, polystyrene, polyacrylate or methacrylate,
melamine formaldehyde resin, polyethylene terephthalate, nylons and
polyurethanes.
As colorants used in the present invention, any of those known in
the art may be used. Stated specifically, those given below may be
used. Carbon black, aniline black, acetylene black, magnetic
materials, and colorants toned in black by the use of yellow,
magenta and cyan colorants shown below may be used as black
colorants.
As yellow colorants usable in the present invention, compounds
typified by condensation azo compounds, isoindolinone compounds,
anthraquinone compounds, azo metal complexes, methine compounds and
allylamide compounds are used. Stated specifically, e.g., C.I.
Pigment Yellow 12, 13, 14, 15, 16, 17, 62, 74, 83, 93, 94, 95, 97,
109, 110, 111, 120, 127, 128, 129, 147, 168, 174, 176, 180, 181 and
191 are preferably used.
As magenta colorants usable in the present invention, condensation
azo compounds, diketopyropyyrole compounds, anthraquinone
compounds, quinacridone compounds, basic dye lake compounds,
naphthol compounds, benzimidazolone compounds, thioindigo compounds
and perylene compounds are used. Stated specifically, e.g., C.I.
Pigment Red 1, 2, 3, 5, 6, 7, 23, 48:2, 48:3, 48:4, 57:1, 81:1,
144, 146, 166, 169, 177, 184, 185, 202, 206, 220, 221 and 254 are
particularly preferably used.
As cyan colorants usable in the present invention, copper
phthalocyanine compounds and derivatives thereof, anthraquinone
compounds and basic dye lake compounds may be used. Stated
specifically, C.I. Pigment Blue 1, 2, 7, 15:1, 15:2, 15:3, 15:4,
60, 62 and 66 are particularly preferred.
These colorants may be used alone, in the form of a mixture, or in
the solid solution state. When a magnetic material is used as the
colorant, it may preferably be added in an amount of from 40 to 50
parts by weight based on 100 parts by weight of the binder resin.
When other colorant is used, it may preferably be added in an
amount of from 0.1 to 20 parts, and more preferably from 2 to 10
parts by weight, based on 100 parts by weight of the binder
resin.
The toner of the present invention may also be incorporated with a
magnetic material so that it can be used as a magnetic toner. In
this case, the magnetic material may also serve as the colorant.
The magnetic material usable in the present invention may include
iron oxides such as magnetite, hematite and ferrite; metals such as
iron, cobalt and nickel, or alloys of any of these metals with a
metal such as aluminum, cobalt, copper, lead, magnesium, tin, zinc,
antimony, beryllium, bismuth, cadmium, calcium, manganese,
selenium, titanium, tungsten or vanadium, and mixtures of any of
these.
The magnetic material used in the present invention may preferably
be a surface-modified magnetic material. It is particularly
preferable to use materials having been subjected to hydrophobic
treatment with a surface modifier having no polymerization
inhibitory action. Such a surface modifier may include, e.g.,
silane coupling agents and titanium coupling agents.
These magnetic materials may have an average particle diameter of 1
.mu.m or less, and preferably from 0.1 to 1 .mu.m. As the magnetic
material, it is preferable to use those having a coercive force
(Hc) of from 20 to 300 oersted, a saturation magnetization
(.sigma.s) of from 50 to 200 emu/g and a residual magnetization
(.sigma.r) of from 2 to 20 emu/g, as magnetic characteristics under
application of 10 K oersted.
The wax according to the present invention may preferably be, in
cross-sectional observation of toner particles with a transmission
electron microscope (TEM), dispersed in the binder resin in the
form of, substantially, a spherical and/or spindle-shaped island or
islands in such a state that the wax and the binder resin are not
soluble in each other. Typical examples are shown in FIGS. 11A and
11B.
Since the wax is dispersed in the above manner to be embraced in
toner particles, the compound represented by Formula (A) according
to the present invention can be allowed to be present in the
vicinity of the toner particle surfaces in a good efficiency, and
hence the charge controllability inherent in the compound can be
well exhibited. Also, the prevention of deterioration of toner and
the matching to image forming apparatus can be improved, and hence
good charging performance can be maintained, so that toner images
having superior dot reproduction can be formed over a long period
of time. Moreover, the wax can act in a good efficiency at the time
of heat-fixing, and hence satisfactory low-temperature fixing
performance and anti-offset properties can be attained.
In the present invention, the state of dispersion of the wax as in
the above is defined in the following way: Of toner particles
having length of from D4.times.0.9 to D4.times.1.1 with respect to
a weight-average particle diameter D4 (.mu.m) of toner as measured
in the manner as described previously, twenty (20) planes of cross
sections are picked up. Then, a length R of each toner particle
cross-sectional plane thus picked up and a length r of the largest
island in the phase-separated structure ascribable to the wax
present in the toner particle cross-sectional plane having the
length R are measured to determine the arithmetic mean value of
r/R, (r/R).sub.st. When the resultant arithmetic mean value of r/R,
(r/R).sub.st, satisfies 0.05.ltoreq.(r/R).sub.st .ltoreq.0.95, the
wax is regarded as being in the form of, substantially, a spherical
and/or spindle-shaped island or islands in such a state that the
wax and the binder resin are not soluble in each other.
When the wax is so dispersed that the arithmetic mean value of r/R,
(r/R).sub.st, satisfies 0.05.ltoreq.(r/R).sub.st .ltoreq.0.95, the
compound represented by Formula (A) can be made localized to the
toner particle surfaces in a good efficiency, so that the charging
performance of toner can be stabilized. Since the wax is embraced
in toner particles, the toner particle surfaces can be prevented
from deteriorating or the image forming apparatus can be prevented
from being contaminated, and thus, the effect of keeping the
Formula (A) compound in the vicinity of toner particle surfaces can
be maintained. In addition, an instance where the wax is dispersed
in such a state that the arithmetic mean value of r/R,
(r/R).sub.st, satisfies 0.25.ltoreq.(r/R).sub.st .ltoreq.0.95 is
preferred because good charging performance can be maintained and
toner images having superior dot reproduction can be formed over a
long period of time. Since the wax can act in a good efficiency at
the time of heat-fixing, satisfactory low-temperature fixing
performance and anti-offset properties can be attained.
As a method for the cross-sectional observation of toner particles,
it is preferable to use an electron dyeing method in which a
contrast is formed between materials by allowing one of the
materials to have higher electron density than another by the use
of heavy metal, utilizing a difference in the micro-structure of a
crystal layer and an amorphous phase between the wax used and the
resin constituting the shell. Stated specifically, toner particles
are well dispersed in a room-temperature curing epoxy resin,
followed by curing in an environment of temperature 40.degree. C.
for 2 days, the resulting cured product is electron-dyed with
ruthenium tetraoxide (RuO.sub.4) and optionally in combination with
osmium tetraoxide (OsO.sub.4), and thereafter samples are cut into
slices by means of an ultra microtome having a diamond cutter,
observing the cross-sectional form of toner particles using a
transmission electron microscope (TEM).
By the above method, polar resin thin layers present on the toner
particle surfaces can also be observed.
As the wax used in the present invention, any known waxes usable in
toner may be used, which may include, e.g., paraffin wax and
derivatives thereof, montan wax and derivatives thereof,
microcrystalline wax and derivatives thereof, Fischer-Tropsch wax
and derivatives thereof, polyolefin wax and derivatives thereof,
polyester wax and derivatives thereof, ester wax and derivatives
thereof, vegetable waxes and derivatives thereof, animal waxes and
derivatives thereof, and mineral waxes and derivatives thereof, and
petrolactams. The derivatives include oxides, alkylene oxide
addition products, saponified products and salts.
In particular, waxes preferably usable are low-molecular weight
polyalkylene wax, low-molecular weight polyester wax, ester wax,
and aromatic derivatives.
From these waxes, waxes may be fractionated according to the size
of molecular weight by press sweating, solvent fractionation,
vacuum distillation, ultracritical gas extraction or fractionation
recrystallization (e.g., molten liquid crystallization and crystal
filtration). Such waxes may also preferably be used in the present
invention. After the fractionation, they may be subjected to block
copolymerization or graft modification.
For the wax used in the present invention, it is preferred that, in
the DSC curve as measured with a differential scanning calorimeter,
a maximum endothermic peak at the time of temperature rise is
within the region of from 50 to 100.degree. C. and the on-set
temperature at the starting point of a endothermic curve including
the maximum endothermic peak is 40.degree. C. or above. In
particular, it is preferred that the temperature difference between
the peak temperature of the maximum endothermic peak and the on-set
temperature is within the range of from 5 to 50.degree. C.
When the wax having thermal properties as described above is used,
the resulting toner has a good fixing performance as a matter of
course, the release effect attributable to the wax is exhibited in
a good efficiency, a sufficient fixing region is ensured, and also
any bad influence of conventionally known waxes on blocking
resistance and image forming apparatus can be eliminated. Hence,
the effect attributable to the compound represented by Formula (A)
according to the present invention can be well brought out.
Especially, since specific surface area of toner particles
decreases as the toner particle shape is made spherical, it is very
effective to control the thermal properties and dispersion state of
the wax.
In the present invention, the thermal properties of the wax is
measured according to ASTM D3418-82, using, e.g., a differential
scanning calorimeter DSC-7, manufactured by Perkin Elmer Co. The
temperature at the detecting portion of the device is corrected on
the basis of melting points of indium and zinc, and the calorie is
corrected on the basis of the heat fusion of iridium. In the
measurement, a sample is put in a pan made of aluminum and an empty
pan made of aluminum is set as a control. A DSC curve is used which
is obtained when temperature is raised at a temperature rise rate
of 10.degree. C./min in the temperature region of from 20.degree.
C. to 180.degree. C. Here, when the measurement is made on the wax
component alone, the temperature is previously raised-and-dropped
once under the same conditions as those at the time of measurement,
and measurement is started after the pre-history the wax component
has is removed. When the measurement is made on the wax component
kept in toner particles, the measurement is made without the
operation of removing the pre-history.
The wax may preferably be used in an amount of from 3 to 40 parts
by weight, and more preferably from 5 to 35 parts by weight, based
on 100 parts by weight of the binder resin.
As the ester wax, ester waxes having ester compounds satisfying the
following general formula are preferred.
wherein R.sub.1 and R.sub.2 each represent a hydrocarbon group
having 15 to 45 carbon atoms.
The ester wax may further preferably be an ester wax which contains
the ester compounds represented by the above formula and in which
ester compounds having the same number of carbon atoms in total are
in a content ranging from 50 to 95% by weight.
In the present invention, the content of the ester compounds having
the same number of carbon atoms in total are measured by gas
chromatography (GC) described below.
In the present invention, a gas chromatogram is obtained by
measurement with GC-17A (manufactured by Shimadzu Corporation). In
this measurement, a solution previously dissolved in toluene in a
concentration of 1% by weight is used as a sample, and 1 .mu.l of
the sample is injected into a GC system having an on-column
injector. As a column, Ultra Alloy-1 (HT) 0.5 mm in diameter and 10
mm in length is used. The column is kept at an initial temperature
of 40.degree. C., from which the temperature is raised to
200.degree. C. at a rate of 40.degree. C./min, and is further
raised to 350.degree. C. at a rate of 15.degree. C./min, and still
further raised to 450.degree. C. at a rate of 7.degree. C./min. As
a carrier gas, He gas is flowed under a pressure of 50 kPa. When
the types of compounds are identified, an alkane having a known
number of carbon atoms is injected and the measurement is made in
the same flow-out time as the above, identifying their structures
by comparing the resulting gas chromatograms with each other or
introducing gasified components into mass spectrography. Each
content of the ester compounds having the same number of carbon
atoms is calculated by determining the ratio of each peak area to
the total peak area of chromatograms.
An example of a chromatogram of the ester wax is shown in FIG. 1.
As can be seen from FIG. 1, ester compounds as shown below, having
38 carbon atoms in total, are contained in an amount of about 0.6%
by weight;
ester compounds as shown below, having 40 carbon atoms in total,
are contained in an amount of about 5.8% by weight;
ester compounds as shown below, having 42 carbon atoms in total,
are contained in an amount of about 19.0% by weight;
ester compounds as shown below, having 44 carbon atoms in total,
are contained in an amount of about 72.9% by weight;
and further, ester compounds as shown below, having 46 carbon atoms
in total, are contained in an amount of about 1.7% by weight.
With regard to the ester wax used in the above measurement, it has
been ascertained that ester compounds as shown blow, having 44
carbon atoms in total, are contained in an amount of about 72.6% by
weight as the main component.
Ester waxes particularly preferably used as the ester wax are
commonly synthesized from higher carboxylic acid components as in
the case of higher alcohol components. Usually, these higher
alcohol components or higher carboxylic acid components are often
obtained from natural products, and are commonly constituted of
mixtures having an even number of carbon atoms. When such mixtures
are esterified as they are, by-products having various analogous
structures other than the intended ester compounds are formed, and
hence they tend to adversely affect various performances of the
toner. Accordingly, in the present invention, it is preferable to
use ester waxes obtained by purifying raw materials or products by
solvent extraction or vacuum distillation.
In the measurement by the gas chromatography described above, those
in which ester compounds having the same number of carbon atoms in
total are in a content less than 50% by weight may cause
complicated crystal polymorphism or freezing-point depression.
Hence, if such ester compounds are incorporated in toner particles,
they tend to provide a cause of an ill effect chiefly on the
blocking resistance and charge developing performance of the toner.
Moreover, if such ester compounds are used in the present
invention, a stated fluidity of the toner may be hard to attain, or
filming ascribable to ester wax tends to occur on the surfaces of
carrier particles and photosensitive member, so that the quantity
of triboelectricity of the toner may decrease, making it difficult
to attain a sufficient quantity of triboelectricity
continually.
As the ester wax, it is preferable to use those in which the ester
compounds having the same number of carbon atoms in total may
preferably be in a content of from 55 to 95% by weight, and more
preferably from 60 to 95% by weight. It is also preferable to use
those in which the total content of ester compounds including ester
compounds having the same number of carbon atoms in total,
contained in the ester wax in the largest quantity, and ester
compounds having the number of carbon atoms in total within the
range of .+-.2 with respect to the former number of carbon atoms is
preferably from 80 to 95% by weight, and more preferably from 90 to
95% by weight.
When the toner of the present invention is made up, the most
preferable ester wax is one in which the ester compounds having 44
carbon atoms in total as stated above are contained in an amount of
from about 50 to 95% by weight
The ester compounds represented by the above general formula may
include the following ester compounds. ##STR14##
For the ester wax, it is preferred that the peak temperature of a
maximum endothermic peak in the DSC curve is within the region of
from 40 to 90.degree. C., and more preferably from 55 to 85.degree.
C., in view of the improvement of low-temperature fixing
performance and anti-offset properties of the toner.
More specifically, ester waxes in which the peak temperature is
lower than 40.degree. C. have so weak a self cohesive force in
themselves that they tend to cause a lowering of high-temperature
anti-offset properties of the toner. On the other hand, in the case
of ester waxes in which the peak temperature is higher than
40.degree. C., having a high melting point, the ester wax having
such a high peak temperature may be deposited during granulation
because granulation and polymerization are well carried out in an
aqueous medium when toner particles are directly obtained by
polymerization, tending to make it difficult to carry out
granulation in a sharp particle size distribution.
It is preferred that the ester wax has a hardness of from 0.5 to
5.0. The hardness of the ester wax is a value obtained by preparing
a cylindrical sample 20 mm in diameter and 5 mm in wall thickness
and then measuring its Vickers hardness using a dynamic ultrafine
hardness meter (DUH-200) manufactured by Shimadzu Corporation. As
conditions for measurement, using a penetrator, its position is
moved by 10 .mu.m under a load of 0.5 g at a loading rate of 9.67
mg/sec. Thereafter, it is kept as it is for 15 seconds, and a
depression made on the sample is analyzed to determine Vickers
hardness.
According to studies made by the present inventors, the use of
ester waxes whose hardness measured by the above method is less
than 0.5 is large in dependence on the pressure and process speed
of fixing assemblies, tending to cause a lowering of the effect of
high-temperature anti-offset properties. On the other hand, the use
of ester waxes whose hardness is more than 5.0 results in a low
storage stability of the toner, and also tend to cause a lowering
of high-temperature anti-offset properties because such ester waxes
themselves have a small self cohesive force.
The ester wax may preferably have a weight-average molecular weight
(Mw) of from 200 to 2,000 and a number average molecular weight
(Mn) of from 150 to 2,000, and more preferably Mw of from 300 to
1,000 and Mn of from 250 to 1,000. More specifically, when using
ester waxes whose Mw is less than 200 and Mn is less than 150, the
blocking resistance of the toner may be lowered and low molecular
weight components are liable to be present on toner particle
surfaces, resulting in a low fluidity of the toner. On the other
hand, when using ester waxes whose Mw is more than 2,000 and Mn is
more than 2,000, granulation performance is inhibited in the toner
production, tending to cause coalescence of toner particles.
In the present invention, the molecular weight distribution of the
wax is measured by GPC (gel permeation chromatography) under
conditions shown below.
GPC Measurement Conditions
Apparatus: GPC-150C (Waters Co.)
Columns: GMH-HT 30 cm, combination of two columns (available from
Toso Co., Ltd.)
Temperature: 135.degree. C.
Solvent: o-Dichlorobenzene (0.1% ionol-added)
Flow rate: 1.0 ml/min
Sample: 0.4 ml of 0.15% sample is injected.
Molecular weights are measured under conditions shown above. The
molecular weight of the sample is calculated using a molecular
weight calibration curve prepared from a monodisperse polystyrene
reference sample. It is further calculated by converting the value
into polyethylene according to a conversion expression derived from
the Mark-Houwink viscosity equation.
As other additives incorporated in the toner, those shown below for
example may be used for the purpose of imparting various properties
to the toner. As lubricants, preferably usable are powders of
fluorine resins such as polyvinylidene fluoride and
polytetrafluoroethylene, and fatty acid metal salts such as zinc
stearate and calcium stearate. As charge-controllable particles,
preferably usable are metal oxides such as tin oxide, titanium
oxide, zinc oxide, silicon oxide and aluminum oxide, and carbon
black. These additives may be used in an amount of from 0.1 to 10
parts by weight, preferably from 0.1 to 5 parts by weight, based on
100 parts by weight of the binder resin.
The toner of the present invention, when used as a developer, may
preferably be incorporated with an inorganic fine powder (e.g.,
fine silica powder, fine titania powder and fine alumina powder)
having a specific surface area of 30 m.sup.2 /g or above as
measured by nitrogen gas absorption according to the BET method,
and made to have a degree of aggregation of toner in the range of
from 1 to 20%. The reason is that when the developer is prepared
using the inorganic fine powder controlled to have the specific
surface area as described above, the compound represented by
Formula (A) present in the vicinity of toner particle surfaces and
the inorganic fine powder interact so that the water adsorption to
toner particles is controlled more remarkably, bringing about a
greater effect of restraining the quantity of triboelectricity or
charging rate from lowering. The interaction between that compound
and the inorganic fine powder also brings about a greater effect of
preventing the toner carrying member from being contaminated with
that compound. Moreover, the controlling of the degree of
aggregation of toner can regulate the contact state between the
toner particles and the inorganic fine powder, so that the above
mertorious effect can be maintained during continuous copying.
The inorganic fine powder used in the present invention may
preferably have a specific surface area of 30 m.sup.2 /g or above
as described above, and more preferably in the range of from 50 to
400 m.sup.2 /g. That is, an inorganic fine powder having a specific
surface area below 30 m.sup.2 /g makes it difficult to control the
aggregation degree of toner. Also, when the compound represented by
Formula (A) according to the present invention is present on the
toner particle surfaces, the potions where the inorganic fine
powder interacts with the compound may become saturated. If the
inorganic fine powder has a specific surface area above 400 m.sup.2
/g, the inorganic fine powder is buried in the toner particle
surfaces to change the aggregation degree of toner with time in
some cases. The specific surface area is measured according to the
BET method, where nitrogen gas is adsorbed on sample surfaces using
a specific surface area measuring device AUTOSOBE 1 (manufactured
by Yuasa Ionics Co.), and the specific surface area is calculated
by the BET multiple point method.
If the inorganic fine powder, which is externally added, is added
in an mount less than 0.5 part by weight, it may be difficult to
control the aggregation degree of toner. If it is in an amount more
than 5 parts by weight, free inorganic fine powder may contaminate
the toner carrying member and so forth.
For the purposes of making hydrophobic and control of
chargeability, the inorganic fine powder used in the present
invention may preferably be treated, if necessary, with a treating
agent such as silicone varnish, modified silicone varnish of
various types, silicone oil, modified silicone oil of various
types, a silane coupling agent, a silane coupling agent having a
functional group, or other organosilicon compound. Especially in
order to maintain a high charge quantity and achieve a low
consumption and a high transfer efficiency, the inorganic fine
powder may preferably be treated with silicone oil.
The toner of the present invention may be used as a one-component
developer as it is, or may be used in combination with a carrier so
as to be used as a two-component developer.
When used as the two-component developer, for example, a magnetic
carrier blended with the toner may be made of an element selected
from iron, copper, zinc, nickel, cobalt, manganese and chromium,
alone or in the composite ferrite state. The magnetic carrier used
here may be in any shape, e.g., spherical, flat or shapeless. A
magnetic carrier whose particle surface microstructure (e.g.,
surface unevenness) has appropriately been controlled may also be
used. The carrier used may have an average particle diameter of
from 10 to 100 .mu.m, and more preferably from 20 to 50 .mu.m. In
addition, when such a carrier and the toner are blended to prepare
the two-component developer, the toner in the developer may
preferably be in a concentration of from about 2 to 15% by
weight.
As methods for producing the toner of the present invention, any
known methods may be used, such as a pulverization method in which
the binder resin, the colorant, the wax and so forth are
melt-kneaded by means of a pressure kneader, thereafter the kneaded
product is cooled and then pulverized to have the desired toner
particle diameter, and the pulverized product is further brought to
classification to adjust its particle size distribution to produce
a toner; the method as disclosed in Japanese Patent Publication No.
36-10231, and Japanese Patent Applications Laid-Open No. 59-53856
and No. 59-61842, in which toner is directly produced by suspension
polymerization; such a method as disclosed in Japanese Patent
Publication No. 56-13945, in which a melt-kneaded product is
atomized in the air by means of a disk or a multiple fluid nozzle
to obtain spherical toner particles; and an emulsion polymerization
method as typified by soap-free polymerization. It is preferable to
produce a shape-controlled toner by suspension polymerization while
controlling the polymerization conversion of polymerizable monomers
and the pH of aqueous medium.
More specifically, the compound represented by Formula (A) added in
the toner in order to control the quantity of triboelectricity and
the charging rate has so many hydrophilic functional groups that,
when particles formed by granulation of a polymerizable monomer
composition are polymerized in an aqueous dispersion medium to form
toner particles, it may be dissolved in the aqueous dispersion
medium. The compound thus dissolved does not allow the resulting
toner particles to sufficiently exhibit the effect of improving the
charge quantity and charging rate. Also, the compound dissolved
behaves like a surface-active agent to make it very difficult for
the toner particles to retain their shape in the step of
polymerization, so that the toner can not be made to have the
desired particle size distribution and particle shape. Especially
when the compound is dissolved in a large quantity, particles
having a finer particle diameter than the toner particles may be
formed secondarily to bring about a difficulty in the matching to
image forming apparatus.
To solve such a problem, the polymerization conversion of
polymerizable monomers and the pH of aqueous medium may be
controlled, whereby the compound can be prevented from dissolving
and the compound can be retained in the vicinity of toner particle
surfaces in a good state.
Stated in detail, in the polymerization reaction of the
polymerizable monomer composition, a first reaction step is taken
to make the polymerization conversion of polymerizable monomers
higher by at least 10% while keeping the pH of the aqueous medium
at 4.5 to 8.5, and preferably 4.5 to 6.0, whereby the compound
represented by Formula (A) is prevented from dissolving in the
aqueous medium and is embraced in toner particles. Then, the pH of
the aqueous medium is again adjusted to 9 to 13 after the first
reaction step, and a second reaction step is taken to make the
polymerization conversion still higher, whereby the compound
represented by Formula (A) can be drawn out to the vicinity of the
surfaces of toner particles capable of participating in
triboelectric charging and simultaneously the compound present on
the surfaces can be dissolved and removed under alkaline
conditions.
Thus, the compound represented by Formula (A) can be kept in the
vicinity of toner particle surfaces in a good state, so that the
resulting toner can have a very good charging performance. Also,
the particle size distribution and shape of the toner particles can
be controlled as desired, without causing any secondary formation
of particles with fine
particle diameter. Hence, the charging performance can be improved
cooperatively and also the matching to image forming apparatus can
be made very well. Especially when the pH of the aqueous medium in
the first reaction step is kept at 4.5 to 6.0, the compound can be
embraced more in toner particles, and hence the effect of
improvement as stated above can be made much better.
In the present invention, the "polymerization conversion" of
polymerizable monomers is found according to the following
expression by determining a total weight (W2) of unreacted
polymerizable monomers on the basis of a total weight (W1) of
polymerizable monomers used in the polymerizable monomer
composition. Polymerization conversion (%) (W1-W2)/W1.times.100
The unreacted polymerizable monomers can be determined by adding,
immediately after sampling from a reaction vessel, a short-stop
(polymerization terminator) or cold methanol to the collected
sample to terminate the polymerization reaction, and by using a
known method such as (i) a method making use of thermogravimetry
(TG) which makes measurements as a weight loss at the time of
heating by means of a thermobalance, or (ii) a method making use of
gas chromatography (GC). In particular, the method making use of GC
is an especially effective method.
An example in which the polymerizable monomers in the toner are
determined by GC is shown below.
GC Measurement Conditions
Apparatus:
GC-14A (manufactured by Shimadzu Corporation)
Column:
Fused silica capillary column (manufactured by J & W Scientific
Co; size: 30 m.times.0.249 mm; liquid phase: DBWAX; layer
thickness: 0.25 .mu.m)
Sample:
Using 2.55 mg of DMF as an internal reference, a solvent containing
the internal reference is prepared by adding 100 ml of acetone.
Next, 400 mg of toner is made into a 10 ml solution using the
solvent. After treatment with an ultrasonic shaker for 30 minutes,
the solution is left standing for 1 hour. Next, the solution is
filtered with a 0.5 .mu.m filter. The sample is injected in an
amount of 4 .mu.l.
Detector: FID (split ratio: 1:20)
Carrier gas: N.sub.2 gas
Oven temperature:
70.degree. C..fwdarw.220.degree. C. (temperature rise at a rate of
5.degree. C./min after standing at 70.degree. C. for 2 minutes)
Injection temperature: 200.degree. C.
Detection temperature: 200.degree. C.
Preparation of calibration curve:
A reference sample prepared by adding a target polymerizable vinyl
monomer to the same DMF-acetone solution as the sample solution is
similarly measured by gas chromatography to determine the value of
weight ratio/area ratio of the polymerizable vinyl monomer and the
internal reference DMF.
In the present invention, when the toner is produced by suspension
polymerization, any known inorganic or organic dispersant may be
used as a dispersant used when the aqueous dispersion medium is
prepared. Stated specifically, the dispersant used may include, as
inorganic dispersants, e.g., tricalcium phosphate, magnesium
phosphate, aluminum phosphate, zinc phosphate, magnesium carbonate,
calcium carbonate, calcium hydroxide, magnesium hydroxide, aluminum
hydroxide, calcium metasilicate, calcium sulfate, barium sulfate,
bentonite, silica and alumina. As organic compounds, it may
include, e.g., polyvinyl alcohol, gelatin, methyl cellulose, methyl
hydroxypropyl cellulose, ethyl cellulose, carboxymethyl cellulose
sodium salt, and starch.
Commercially available nonionic, anionic or cationic surface active
agents may also be used. For example, usable are sodium
dodecylsulfate, sodium tetradecylsulfate, sodium pentadecylsulfate,
sodium octylsulfate, sodium oleate, sodium laurate, potassium
stearate and calcium oleate.
In the present invention, a slightly water-soluble dispersant of an
inorganic type is preferred, and besides a slightly water-soluble
inorganic dispersant which is soluble in acid may preferably be
used. In the present invention, when the aqueous dispersion medium
is prepared using the slightly water-soluble inorganic dispersant,
such a dispersant may preferably be used in a proportion of from
0.2 to 2.0 parts by weight based on 100 parts by weight of the
polymerizable monomers. Also, in the present invention, the aqueous
dispersion medium may preferably be prepared by using water in an
amount of from 300 to 3,000 parts by weight based on 100 parts by
weight of the polymerizable monomer composition.
In the present invention, when the aqueous dispersion medium in
which the slightly water-soluble inorganic dispersant as described
above has been dispersed is prepared, a commercially available
dispersant may be used as it is, to make dispersion. In order to
obtain dispersant particles having fine and uniform particle size,
such a slightly water-soluble inorganic dispersant may be prepared
by forming it in a liquid medium such as water under high-speed
stirring. For example, when tricalcium phosphate is used as the
dispersant, an aqueous sodium phosphate solution and an aqueous
calcium chloride solution may be mixed to from fine particles of
tricalcium phosphate, thus a preferable dispersant can be
obtained.
The toner production process of the present invention, which is
comprised as described above, can readily provide a toner which can
restrain the decrease in quantity of triboelectricity in a high
humidity environment and the lowering of the triboelectric charging
rate in a low humidity environment, which have conventionally
occurred in toners containing charge control agents, and also can
effectively restrain the toner carrying member from being
contaminated.
The image forming method to which the toner of the present
invention is applied will be described below with reference to the
accompanying drawings.
In the apparatus system shown in FIG. 2, a developer having a cyan
toner, a developer having a magenta toner, a developer having a
yellow toner and a developer having a magnetic black toner are put
into developing assemblies 4-1, 4-2, 4-3 and 4-4, respectively.
Electrostatic latent images formed on an electrostatic latent image
bearing member (e.g., photosensitive drum) 1 are developed by
magnetic brush development or non-magnetic one-component
development to form toner images of respective colors on the
photosensitive drum 1.
The toner of the present invention may be blended with a magnetic
carrier so that development can be made using, e.g., a developing
means of a two-component development system as shown in FIG. 3.
Stated specifically, the development may preferably be carried out
while applying an alternating electric field and in such a state
that a magnetic brush formed of the toner and the magnetic carrier
comes into touch with a photosensitive drum 13. A distance B
between a developer carrying member (developing sleeve) 11 and the
photosensitive drum 13 (distance between S-D) may preferably be
from 100 to 1,000 .mu.m. This is desirable for preventing carrier
adhesion and improving dot reproducibility. If it is smaller (i.e.,
the gap is narrower) than 100 .mu.m, the developer tends to be
insufficiently fed, resulting in a low image density. If it is
larger than 1,000 .mu.m, the magnetic line of force from the
magnetic pole S1 held by a magnetism generating means 14 internally
provided for the developing sleeve may broaden to make the magnetic
brush have a low density, resulting in a poor dot reproducibility,
or to weaken the force of binding the carrier, tending to cause
carrier adhesion.
The alternating electric field may preferably be applied at a
peak-to-peak voltage (Vpp) of from 500 to 5,000 V and a frequency
(f) of from 500 to 10,000 Hz, and preferably from 500 to 3,000 Hz,
which may each be applied to the process under appropriate
selection. In this instance, the waveform used may be selected from
triangular waveform, rectangular waveform, sinusoidal waveform, or
waveform with a varied duty ratio. If the peak-to-peak voltage is
lower than 500 V, a sufficient image density may be hard to attain,
and fog toner at non-image areas cannot be satisfactorily collected
in some cases. If the peak-to-peak voltage is higher than 5,000 V,
the electrostatic latent image may be disordered through the
magnetic brush to cause a lowering of image quality.
The use of a two-component developer having a toner desirably
charged enables fog take-off voltage (Vback) to be lowered, and
enables the photosensitive member to be low charged in its primary
charging, thus the photosensitive member can be made to have a
longer lifetime. While depending upon development systems, the
Vback may preferably be 150 V or below, and more preferably 100 V
or below.
As contrast potential, a potential of from 200 V to 500 V may
preferably be used so that a sufficient image density can be
achieved.
If the frequency (f) is lower than 500 Hz, electric charges may be
injected into the carrier, relating also to process speed, so that
carrier adhesion may occur or latent images may be disordered,
causing a lowering of image quality. If the frequency (f) is higher
than 10,000 Hz, the toner can not follow up the electric field to
tend to cause a lowering of image quality.
In order to carry out development promising a sufficient image
density, achieving a superior dot reproducibility and free of
carrier adhesion, the magnetic brush on the developing sleeve 11
may preferably be made to come into touch with the photosensitive
drum 13 at a width (developing nip C) of from 3 to 8 mm. If the
developing nip C is narrower than 3 mm, it may be difficult to
satisfy sufficient image density and dot reproducibility. If it is
broader than 8 mm, the developer may be packed into the nip to
cause the machine to stop from operating, or it may be difficult to
well prevent the carrier adhesion. As methods for adjusting the
developing nip, the nip width may appropriately be adjusted by
adjusting the distance A between a developer-regulating blade 18
and the developing sleeve 11, or by adjusting the distance B
between the developing sleeve 11 and the photosensitive drum
13.
In the formation of full-color images which attaches importance
especially to halftones, three or more developing assemblies for
magenta, cyan and yellow may be used, and the developer and
developing process making use of the toner of the present invention
may be used, especially in combination with a development system in
which digital latent images are formed. Thus, the latent images are
not affected by the magnetic brush and are not disordered, and
hence can be developed faithfully to the dot images. Also in the
transfer step, the use of the toner of the present invention
enables a high transfer efficiency to be achieved, and therefore
enables a high image quality to be achieved in both halftone areas
and solid areas.
In addition, concurrently with the achievement of a high image
quality at the initial stage, the effect of the present invention
can be continuously exhibited without any lowering of image quality
even in many-sheet copying.
The toner of the present invention may preferably be used also in
one-component development. An example of an apparatus for
developing electrostatic latent images formed on the electrostatic
latent image bearing member by the use of a one-component developer
is shown below. Examples are not necessarily limited to the
following.
In FIG. 4, reference numeral 20 denotes an electrostatic latent
image bearing member (photosensitive drum). Latent images are
formed by electrophotographic processing means or electrostatic
recording means. Reference numeral 24 denotes a toner carrying
member (developing sleeve) formed of a non-magnetic sleeve made of
aluminum or stainless steel.
Substantially the right half of the periphery of the toner carrying
member 24 always comes into contact with a toner reservoir inside a
toner container 21, and the toner in the vicinity of the toner
carrying member 24 is attracted and held onto the toner carrying
member surface by the aid of a magnetic force and/or electrostatic
force produced by the magnetism generating means provided in the
toner carrying member.
In the present invention, the toner carrying member may preferably
have a surface roughness Ra (.mu.m) so set as to be not larger than
1.5, preferably not larger than 1.0, and more preferably not larger
than 0.5.
When the surface roughness Ra is set to be not larger than 1.5, the
toner particle transporting performance the toner carrying member
has can be controlled, the toner layer formed on the toner carrying
member can be made thinner and also the times the toner carrying
member comes into contact with the toner increases, and hence the
charging performance of the toner can also be improved to
cooperatively bring about an improvement in image quality.
If the toner carrying member has a surface roughness Ra larger than
1.5, not only the toner layer on the toner carrying member is hard
to make thin, but also the charging performance of the toner is not
improved, thus no improvement in image quality can be expected.
In the present invention, the surface roughness Ra of the toner
carrying member corresponds to centerline average roughness
measured using a surface roughness measuring device (SURFCOADER
SE-30H, manufactured by K. K. Kosaka Kenkyusho) according to JIS
surface roughness "JIS B-0601"). Stated specifically, a portion of
2.5 mm is drawn out of the roughness curve, setting a measurement
length a in the direction of its centerline. When the centerline of
this drawn-out portion is represented by X axis, the direction of
lengthwise magnification by Y axis, and the roughness curve by
y=f(x), the value determined according to the following expression
and indicated in micrometer (.mu.m) is the surface roughness Ra.
##EQU4##
As the toner carrying member used in the present invention, a
cylindrical or belt-like member formed of, e.g., a non-magnetic
metal such as stainless steel or aluminum may preferably be used.
If necessary, a metal or resin coat may be provided on the surface
of its substrate, or a resin in which fine particles of resin,
metals, carbon black or charge control agent have been dispersed
may be coated.
In the present invention, the speed of surface movement of the
toner carrying member may be set 1.05 to 3.0 times the speed of
surface movement of the electrostatic latent image bearing member,
whereby the toner layer on the toner carrying member can have an
appropriate agitation effect and hence the faithful reproduction of
the electrostatic latent image can be more improved.
If the speed of surface movement of the toner carrying member is
less than 1.05 times the speed of surface movement of the
electrostatic latent image bearing member, the agitation effect on
the toner layer may become insufficient, so that it can not be
expected to form good images. Also, when images requiring a large
quantity of toner over a wide area are developed as in the case of
solid black images, the quantity of toner fed to the electrostatic
latent image tends to become short, resulting in an insufficient
image density. If on the other hand the speed of surface movement
of the toner carrying member is more than 3.0 times the speed of
surface movement of the electrostatic latent image bearing member,
not only various problems caused by excessive charging of toner as
stated above, but also the deterioration of toner due to mechanical
stress or the sticking of toner to the toner carrying member tends
to occur undesirably.
The toner, T, is stored in a toner container 21, and is fed onto
the developing sleeve 24 by means of a feed member 22. As the feed
member, a feed roller comprised of a porous elastic material as
exemplified by a foamed material such as soft polyurethane foam may
preferably be used. The feed roller may be rotated at a relative
speed that is not zero in the forward direction or backward
direction with respect to the developing sleeve so that the toner
can be fed onto the developing sleeve and also the toner remaining
on the developing sleeve (the toner not participated in
development) can be stripped off. In this instance, taking account
of the balance of the feeding and stripping of the toner, the feed
roller may be brought into contact with the developing sleeve at a
width (a nip) of from 2.0 to 10.0 mm, and more preferably from 4.0
to 6.0 mm. On the other hand, this inevitably imposes an excess
stress to the toner to tend to cause an increase in agglomeration
due to the deterioration of toner, or cause the melt-adhesion or
sticking of toner to the developing sleeve and feed roller.
However, since the toner used in the developing process of the
present invention has excellent fluidity and releasability and has
a
running stability, the toner is preferably usable also in the
developing system having such a feed member. A brush member formed
of resin fiber such as nylon or rayon may also be used as the feed
member. Such a feed member is very effective in a non-magnetic
one-component development carried out using a non-magnetic
one-component developer (non-magnetic toner), in which any magnetic
binding force can not be utilized. It may also be used in a
magnetic one-component development carried out using a magnetic
one-component developer (magnetic toner).
The toner fed onto the developing sleeve is coated in thin layer
and uniformly by a regulation member. The regulation member, 23,
for making thin toner layer may be a doctor blade such as a metal
blade or magnetic blade provided a given interval apart from the
developing sleeve. Alternatively, in place of the doctor blade, a
rigid-material roller or sleeve formed of metal, resin or ceramic
may be used, and a magnetism generating means may be provided in
the inside thereof. Also, an elastic member such as an elastic
blade or an elastic roller for coating the toner under pressure
contact may be used as the regulation member for making thin toner
layer. For example, as shown FIG. 4, an elastic blade 23 is, at its
upper side base portion, fixedly held on the side of the toner
container 21 and is so provided that its blade inner face side (or
its outer face side in the case of the backward direction) is, at
its lower side, brought into touch with the surface of the
developing sleeve 24 under an appropriate elastic pressure in such
a state that it is deflected against the elasticity of the blade in
the forward direction or backward direction of the rotation of the
developing sleeve. According to such construction, a toner layer
can be formed which is stable even in environmental variations and
is dense. The reason therefor is not necessarily clear, and it is
presumed that the toner is forcibly brought into friction with the
developing sleeve surface by the elastic member and hence the toner
is charged always in the like state without regard to any changes
in behavior caused by environmental changes of toner.
On the other hand, the toner tends to be so excessively charged
that it tends to melt-adhere to the developing sleeve or elastic
blade. However, the toner of the present invention can be
preferably used because it has a superior releasability and has a
stable triboelectric chargeability.
As the elastic blade, it is preferable to select a material of
triboelectric series suited for electrostatically charging the
toner to the desired polarity, which includes rubber elastic
materials such as silicone rubber, urethane rubber or NBR;
synthetic resin elastic materials such as polyethylene
terephthalate; and metal elastic materials such as stainless steel,
steel and phosphor bronze, as well as composite materials thereof,
any of which may be used.
In instances where the elastic member and the developing sleeve are
required to have a durability, resin or rubber may preferably be
stuck to, or coated on, the metal elastic material so as to touch
the part coming into contact with the sleeve.
An organic or inorganic substance may also be added to, may be
melt-mixed in, or may be dispersed in, the elastic member. For
example, any of metal oxides, metal powders, ceramics, carbon
allotropes, whiskers, inorganic fibers, dyes, pigments and
surface-active agents may be added so that the charging performance
of the toner can be controlled. Especially when the elastic member
is formed of a molded product of rubber or resin, a fine metal
oxide powder such as silica, alumina, titania, tin oxide, zirconium
oxide or zinc oxide, carbon black, or a charge control agent
commonly used in toners may preferably be incorporated therein.
A DC electric field and/or an AC electric field may also be applied
to a developing blade serving as the regulation member, a feed
roller as the feed member and a brush member, whereby the uniform
thin-layer coating performance and uniform chargeability can be
more improved at the regulated part on the developing sleeve
because of the loosening action acting on the toner and the toner
can be smoothly fed and stripped off, so that a sufficient image
density can be achieved and images with a good quality can be
formed.
It is effective for the elastic member to be brought into touch
with the toner carrying member (developing sleeve) at a pressure of
0.1 kg/m or above, preferably from 0.3 to 25 kg/m, and more
preferably from 0.5 to 12 kg/cm, as a linear pressure in the
generatrix direction of the toner carrying member. This makes it
possible to effectively loosen the agglomeration of toner and makes
it possible to effect instantaneous rise of the charge quantity of
toner. If the touch pressure is below 0.1 kg/m, it is difficult to
uniformly coat the toner, resulting in a broad charge quantity
distribution of the toner to cause fog or black spots around line
images. If the touch pressure is above 25 kg/m, a great pressure is
applied to the toner to cause deterioration of the toner and
occurrence of aggregates of the toner, and also a great torque is
required in order to drive the toner carrying member,
undesirably.
The gap a between the electrostatic latent image bearing member and
the toner carrying member may preferably be set to be from 50 to
500 .mu.m, and the gap between the doctor blade and the toner
carrying member may preferably be set to be from 50 to 400
.mu.m.
The layer thickness of the toner layer formed on the toner carrying
member may preferably be made smaller than the gap a between the
electrostatic latent image bearing member and the toner carrying
member. In some cases, the layer thickness of the toner layer may
be regulated in such an extent that part of a large number of toner
ears constituting the toner layer comes into contact with the
surface of the electrostatic latent image bearing member.
Meanwhile, an alternating electric field may be applied across the
toner carrying member and the electrostatic latent image bearing
member by a bias power source 26. This makes it easy for the toner
to move from the toner carrying member to the electrostatic latent
image bearing member and to form images with a much higher image
quality. The alternating electric field may preferably be applied
at Vpp of 100 V or above, preferably from 200 to 3,000 V, and more
preferably from 300 to 2,000 V. It may also preferably be applied
at a frequency (f) of from 500 to 5,000 Hz, more preferably from
1,000 to 3,000 Hz, and still more preferably from 1,500 to 3,000
Hz. As the waveform of this electric field, rectangular waveform,
sine waveform, sawtooth waveform and triangle waveform may be used.
An asymmetrical AC bias having different time for which
forward/backward voltages are applied may also be used. It is also
preferable to use a bias formed by superimposing an AC bias on to a
DC bias.
In the apparatus shown in FIG. 2, the electrostatic latent image
bearing member 1 is a photosensitive drum or photosensitive belt
having a photoconductive insulating material layer formed of
.alpha.-Se, CdS, ZnO.sub.2, OPC or a-Si. The electrostatic latent
image bearing member 1 is rotatively driven by means of a drive
system (not shown) in the direction of an arrow.
As the electrostatic latent image bearing member 1, a
photosensitive member having an amorphous silicon photosensitive
layer or an organic photosensitive layer may preferably be
used.
The organic photosensitive layer may be of a single-layer type in
which the photosensitive layer contains a charge generating
material and a charge transporting material in the same layer, or
may be a function-separated photosensitive layer comprised of a
charge transport layer and a charge generation layer. A multi-layer
type photosensitive layer comprising a conductive substrate, and
the charge generation layer and the charge transport layer
superposed on the substrate in this order is one of preferred
examples.
As binder resins for the organic photosensitive layer,
polycarbonate resins, polyester resins or acrylic resins may
preferably be used because they provide a good transfer performance
and a good cleaning performance, and may hardly cause faulty
cleaning, melt-adhesion of toner to the photosensitive member and
filming of external additives.
The step of charging has a system in which the charging means and
the electrostatic latent image bearing member 1 are in non-contact
with each other as in a corona charging assembly, or a contact type
system in which they are in contact with each other as in a
charging roller. Either system may be used. The contact charging
system as shown in FIG. 2 may preferably be used so as to enable
efficient and uniform charging, simplify the system and make ozone
less occur.
A charging roller 2 is constituted basically of a mandrel 2b at the
center and a conductive elastic layer 2a that forms the periphery
of the former. The charging roller 2 is brought into pressure
contact with the surface of the electrostatic latent image bearing
member 1 and is rotated following the rotation of the electrostatic
latent image bearing member 1.
When the charging roller is used, the charging process may
preferably be performed under the conditions of a roller contact
pressure of 5 to 500 g/cm, and an AC voltage of 0.5 to 5 kVpp, an
AC frequency of 50 Hz to 5 kHz and a DC voltage of .+-.0.2 to
.+-.1.5 kV when a voltage formed by superimposing an AC voltage on
a DC voltage is applied, and a DC voltage of from .+-.0.2 to .+-.5
kV when only a DC voltage is applied.
As a charging means other than the charging roller, there are a
method making use of a charging blade and a method making use of a
conductive brush. These contact charging means have the effect of,
e.g., making high voltage unnecessary and making ozone less
occur.
The charging roller and charging blade as contact charging means
may preferably be made of a conductive rubber, and a release coat
may be provided on its surface. The release coat may be formed of a
nylon resin, PVDF (polyvinylidene fluoride) or PVDC (polyvinylidene
chloride), any of which may be used.
The toner image on the electrostatic latent image bearing member is
primarily transferred to an intermediate transfer member 5 to which
a voltage (e.g., .+-.0.1 to .+-.5 kV) is applied. The surface of
the electrostatic latent image bearing member is cleaned by a
cleaning means 9 having a cleaning blade 8.
The intermediate transfer member 5 is comprised of a pipe-like
conductive mandrel 5b and a medium-resistance elastic material
layer 5a formed on its periphery. The mandrel 5b may comprise a
plastic pipe provided thereon with a conductive coating.
The medium-resistance elastic material layer 5a is a solid or
foamed-material layer made of an elastic material such as silicone
rubber, Teflon rubber, chloroprene rubber, urethane rubber or EPDM
(an ethylene-propylene-diene terpolymer) in which a
conductivity-providing agent such as carbon black, zinc oxide, tin
oxide or silicon carbide has been mixed and dispersed to adjust
electrical resistance (volume resistivity) to a medium resistance
of from 10.sup.5 to 10.sup.11 .OMEGA..multidot.cm.
The intermediate transfer member 5 is provided in contact with the
bottom part of the electrostatic latent image bearing member, being
axially supported in parallel to the electrostatic latent image
bearing member 1, and is rotatively driven at the same peripheral
speed as the electrostatic latent image bearing member 1 in the
direction as shown by an arrow.
The first-color toner image formed and held on the surface of the
electrostatic latent image bearing member 1 is, in the course of
passing through the transfer nip portion where the electrostatic
latent image bearing member 1 and the intermediate transfer member
5 come into contact with each other, intermediately sequencially
transferred to the periphery of the intermediate transfer member 5
by the aid of the electric filed formed at the transfer nip
portion, by a transfer bias applied to the intermediate transfer
member 5.
If necessary, after the toner image has been transferred to the
transfer medium, the surface of the intermediate transfer member 5
may be cleaned by a detachable cleaning means 10. When the toner is
present on the intermediate transfer member 5, the cleaning means
10 is separated from the surface of the intermediate transfer
member so that the toner image is not disordered.
A transfer means 7 by which the toner image is secondarily
transferred from the intermediate transfer member to the transfer
medium is provided in contact with the bottom part of the
intermediate transfer member 5, being axially supported in parallel
to the intermediate transfer member 5. The transfer means 7 is,
e.g., a transfer roller or a transfer belt, and is rotatively
driven at the same peripheral speed as the intermediate transfer
member 5 in the clockwise direction as shown by an arrow. The
transfer means 7 may be so provided that it comes into direct
contact with the intermediate transfer member 5, or may be so
disposed that a belt comes into contact with and between the
intermediate transfer member 5 and the transfer means 7
therebetween.
In the case of the transfer roller, it is basically comprised of a
mandrel 7b at the center and a conductive elastic layer 7a that
forms the periphery of the former.
The intermediate transfer member and the transfer roller may be
formed of commonly available materials. The elastic layer of the
transfer roller may be made to have a volume resistivity set
smaller than the volume resistivity of the elastic layer of the
intermediate transfer member, whereby the voltage applied to the
transfer roller can be lessened, good toner images can be formed on
the transfer medium and also the transfer medium can be prevented
from being wound around the intermediate transfer member. In
particular, the elastic layer of the intermediate transfer member
may preferably have a volume resistivity at least 10 times the
volume resistivity of the elastic layer of the transfer roller.
For example, a conductive elastic layer 7b of the transfer roller 7
is made of, e.g., an elastic material having a volume resistivity
of 10.sup.6 to 10.sup.10 .OMEGA..multidot.cm, such as polyurethane,
or an ethylene-propylene-diene type terpolymer (EPDM), with a
conductive material, such as carbon, dispersed therein. A bias is
applied to the mandrel 7a by a constant voltage power source. As
bias conditions, a voltage of from .+-.0.2 to .+-.10 kV is
preferred.
The toner image on the transfer medium 6 is fixed by means of a
heat-and-pressure fixing means H. The heat-and-pressure fixing
means may include a heat roll system constituted basically of a
heat roller internally provided with a heating element such as a
halogen heater and an elastic-material pressure roller brought into
contact therewith under pressure, and a system in which the toner
image is fixed by heat and pressure by means of a heater through a
film (FIGS. 5 and 6). The toner of the present invention can well
match the above heat-and-pressure fixing means because of its
superior fixing performance and anti-offset properties.
The toner of the present invention has a high transfer efficiency
at the transfer step, may make the toner less remain after transfer
and also has a superior cleaning performance, and hence the filming
may hardly occur on the electrostatic latent image bearing member.
Moreover, the toner of the present invention may less make the
external additive bury in the toner particle surfaces than
conventional toners even when a many-sheet running test is made,
and hence a good image quality can be maintained over a long period
of time. Accordingly, it is preferably used especially in an image
forming apparatus having what is called the reuse mechanism in
which the toner remaining on the electrostatic latent image bearing
member and intermediate transfer member after transfer is removed
by a cleaning means such as a cleaning blade and the toner
remaining after transfer and thus collected is reused.
The reuse mechanism is described with reference to FIG. 10. The
transfer residual toner present on the surface of a photosensitive
drum 120 after transfer is scraped off with an elastic blade 122
coming into touch with the photosensitive drum, and is collected in
a cleaner 121. The transfer residual toner thus collected is
transported through a cleaner screw 123, by means of a feed pipe
124 provided with a transport screw, and, through a hopper 125,
returned to a developing assembly 126. The toner thus returned is
again used for development.
A one-component contact development system may also be used in
which an elastic roller is used as the toner carrying member, the
toner is coated on the surface of this elastic roller to form a
toner layer and this toner
layer is brought into contact with the surface of the
photosensitive member serving as an image bearing member.
In the one-component contact development system, the toner may be
either of magnetic and non-magnetic, and it is important that the
toner layer and the photosensitive member surface come into contact
with each other. The toner carrying member may preferably
substantially come into contact with the photosensitive member
surface, which means that the toner carrying member comes into
contact with the photosensitive member when the toner layer is
removed from the toner carrying member. Here, in order to obtain
images free of the edge effect through the toner and by the aid of
an electric field acting between the photosensitive member surface
and the toner carrying member facing the photosensitive member
surface, it is necessary for the elastic roller to have a potential
on its surface or in the vicinity of the surface and for the
electric field to be formed between the photosensitive member
surface and the elastic roller toner carrying member surface.
Hence, the elastic layer formed by elastic rubber on the surface of
a low-resistance core material of the elastic roller may be
resistance-controlled in a medium-resistance region so as to keep
the electric field while preventing its conduction with the
photosensitive member surface, or a thin-layer dielectric layer may
be provided on the surface of a low-resistance conductive roller;
either method may be used. The system may also bo so constituted
that a conductive roller is coated with an insulating substance on
its surface side facing the photosensitive member surface or
provided with a conductive layer on the inner side of an insulating
sleeve not facing the photosensitive member.
When the one-component contact development system is used, a
developing roller serving as the toner carrying member for carrying
the toner thereon may be rotated in the same direction as the
photosensitive member (the same surface movement direction), or may
be rotated in the opposite direction. When the developing roller is
rotated in the same direction, it may preferably be rotated at a
peripheral speed ratio of more than 100% with respect to the
peripheral speed of the photosensitive member. If it is not more
than 100%, a problem may be left on image quality, e.g., a poor
line sharpness. With an increase in the peripheral speed ratio, the
quantity of the toner fed to the developing zone increases, and the
toner is more frequently taken on and off the latent image, where
the toner is repeatedly scraped off at the unwanted part and
imparted to the wanted part, so that an image faithful to the
electrostatic latent image can be formed.
The image forming method of the present invention will be described
with reference to the accompanying drawings.
FIG. 7 diagrammatically illustrates, as an example of the
one-component contact development system according to the present
invention, an image forming apparatus having a process
cartridge.
A photosensitive member 56 is electrostatically charged by means of
a charging roller 51 serving as the contact charging means, and
image areas are exposed to laser light 60 to form an electrostatic
latent image. A toner 50 held in a developing assembly 52 is coated
on a toner carrying member 54 by means of a toner coating roller 55
and a coating blade 53, a toner layer formed on the toner carrying
member 54 is brought into contact with the surface of the
photosensitive member 56, and the electrostatic latent image formed
on the photosensitive member 56 is developed by reversal
development, to form a toner image on the photosensitive member 56.
To the toner carrying member 54, at least a DC bias is applied
through a bias applying means 61. The toner image on the
photosensitive member 56 is transferred onto a transfer medium 58
transported to the transfer zone, by means of a transfer roller 57,
serving as the transfer means, to which a bias is applied through a
bias applying means 62. The toner image transferred onto the
transfer medium is fixed through a heat-and-pressure fixing means
63 having a heating roller and a pressure roller.
The image forming apparatus has a blade-like cleaning member 59
provided in contact with the surface of the photosensitive member
56 between the transfer zone assigned to a transfer roller 57 and
the charging zone assigned to a charging roller 51. The transfer
residual toner remaining on the photosensitive member 56 after the
step of transfer is scraped off by the cleaning member 59 and
collected by a cleaner. The photosensitive member 56 from the
surface of which the transfer residual toner has been removed is
again electrostatically charged by the charging roller 51 and is,
after charged, exposed to laser light 60, so that an electrostatic
latent image is formed. The electrostatic latent image on the
photosensitive member 56 is developed by the toner carried on the
developer carrying member 54. A toner image formed on the
photosensitive member 56 after the developing step is transferred
by means of the transfer roller 57 onto a recording medium 58
transported to the transfer zone. After the transfer step, the
photosensitive member 56 is cleaned by the cleaning member 59 to
remove the transfer residual toner, and thereafter again
electrostatically charged by means of the charging roller 51. A
similar process is repeatedly carried out thereafter.
FIG. 8 illustrates another example of the image forming apparatus,
in which the toner can be fed to a developing sleeve serving as the
toner carrying member and in addition thereto the toner having
participated in development can smoothly be stripped off the
developing sleeve.
In FIG. 8, reference numeral 71 denotes a photosensitive drum,
around which a primary charging roller 72 as a contact charging
means, a developing assembly 78 as a developing means, a transfer
charging roller 91 as a contact transfer means and a resistor
roller 89 are provided. Then, the photosensitive drum 71 is
electrostatically charged to, e.g., -700 V by means of the primary
charging roller 72. Voltage applied by a bias applying means 75 is
DC voltage which is, e.g., -1,350 V. Then, the photosensitive drum
71 is exposed to laser light 7 emitted from a laser light generator
76 to form a digital electrostatic latent image. The electrostatic
latent image on the the photosensitive drum 71 is developed by a
non-magnetic one-component developer (toner) 85, and is transferred
onto a recording medium 90 by means of the transfer roller 91 to
which a bias voltage is applied through a bias applying means 94.
The recording medium 90 holding thereon a toner image 96 is
transported on a transfer belt 95 to a heat-and-pressure fixing
assembly 97 having a heat roller 98 and a pressure roller 99, and
the toner image is fixed to the recording medium 90. Reference
numeral 102 denotes a cleaner having a cleaning member 101. The
transfer residual toner on the photosensitive drum after the
transfer step is scraped off by the cleaning member 101 and
collected by the cleaner 102.
The charging roller 72 is basically constituted of a mandrel 74 at
the center and a conductive elastic layer 73 that forms its
periphery.
The developing assembly 78 is, as shown in FIG. 9, provided with a
developing sleeve serving as the toner carrying member, which is an
elastic roller 79 having a mandrel 80 to which a bias voltage is
applied through a bias applying means 88 and an elastic layer 81,
and the toner layer on the developing sleeve 79 comes into contact
with the photosensitive drum 71. Inside the developing assembly 78,
a toner coating roller 82 is provided which has a mandrel 83 to
which a bias voltage is applied through a bias applying means 87
and an elastic layer 84. As a member for regulating the quantity of
the toner transported while attracted onto the developing sleeve
79, a toner regulating blade 86 is provided so that the quantity
(or layer thickness) of the toner transported to the developing
zone can be controlled in accordance with a pressure at which the
toner regulating blade 86 is brought into touch with the developing
sleeve 79. In the developing zone, a DC development bias is applied
at least to the developing sleeve 79, and the toner layer on the
developing sleeve comes into contact with the photosensitive drum
71 surface and is moved onto the photosensitive drum 71 in
accordance with the electrostatic latent image to form a toner
image thereon.
When the photosensitive drum 71 has a light-area potential of from
0 to 250 V and a dark-area potential of from 300 to 1,000 V, a feed
bias voltage applied from the bias applying means 87 may preferably
be from 100 to 900 V and a development bias voltage applied from
the bias applying means 88 may preferably be from 100 to 900 V.
The feed bias voltage applied from the bias applying means 87 may
also preferably be 10 to 400 V, as an absolute value, higher than
the development bias voltage applied from the bias applying means
88. This is preferable because the feeding of the non-magnetic
toner 85 to the developing sleeve 79 and the stripping of the
non-magnetic toner from the developing sleeve 79 can be made
smooth.
In view of the feeding and stripping of the non-magnetic toner, it
is preferable for the toner coating roller 82 to be rotated in the
same direction as the rotational direction of the developing sleeve
79 so that both their surfaces move in the counter direction each
other as shown in arrows in FIG. 9.
In the image forming apparatus shown in FIGS. 7 and 8, the transfer
residual toner not transferred in the transfer step and present on
the surface of the electrostatic latent image bearing member is
removed by bringing the cleaning member into contact with the
surface of the electrostatic latent image bearing member. Another
image forming method employing what is called
"cleaning-at-development system", in which the cleaning for
removing the transfer residual toner is simultaneously performed at
the time of development in the developing step, is also one of
preferred embodiments.
This cleaning-at-development system does not have any cleaning
member provided in contact with the surface of the electrostatic
latent image bearing member between the transfer zone and the
charging zone and between the charging zone and the developing zone
for removing the transfer residual toner present on the surface of
the electrostatic latent image beating member (photosensitive
member).
The charge of the transfer residual toner may change greatly also
in accordance with transfer bias conditions and transfer medium
resistance. As the transfer bias, a voltage having a polarity
reverse to the charge polarity of the toner is commonly applied. In
the case when the development is regular development (the toner
charge polarity is opposite to the photosensitive member charge
polarity) and when the transfer medium is one having a high
resistance, such as cardboards and OHP films, toner particles
having a high charge go forward to the cleaning step while kept at
that charge polarity, without being transferred because of their
strong adhesion to the photosensitive member, and hence the
photosensitive member tends not to be completely cleaned.
Accordingly, the charge of the toner having participated in
development on the photosensitive member may preferably be
controlled to an appropriate quantity so that any toner originally
having a high charge quantity does not participate in development
on the photosensitive member.
In order for the toner with a high charge quantity not to
participate in development on the photosensitive member, it is
necessary to control the charging of the toner or the charging
performance of the toner. However, insufficient charging of the
toner tends to cause problems such as toner scatter and a lowering
of transfer performance of the toner.
In the toner according to the present invention, since the compound
represented by Formula (A) is incorporated in toner particles, it
has become possible to restrain toner particles from being
excessively charged and to provide the toner with an appropriate
charge quantity. Thus, the toner exhibits a stable performance with
a superior running performance also in the developing step.
On the other hand, in the case where the development is reversal
development (the toner charge polarity is the same polarity as the
photosensitive member charge polarity), if the transfer medium is
one readily passing through electric fields, such as thin paper,
toner particles are strongly charged in a reverse polarity by
transfer bias, and the toner particles strongly charged in a
reverse polarity have a strong adhesion to the photosensitive
member, and hence the photosensitive member tends not to be
completely cleaned.
To solve this problem, the toner incorporated with the compound
represented by Formula (A) is used in the present invention, thus
it has become possible to restrain toner particles from being
excessively reverse-charged. In addition, the use of the toner
incorporated with the compound represented by Formula (A) according
to the present invention makes it easy to control the toner charge
quantity affected by transfer bias.
The reason therefor is not necessarily clear, and is presumed
according to findings by the present inventors that the compound
represented by Formula (A) prevents a charge-up phenomenon, in
which the toner is excessively charged in a high quantity, and also
makes it hard for toner particles to hold any excessive reverse
charge even when an electric field reverse to the charge polarity
of the toner is applied in the transfer step.
The principle of the cleaning-at-development system is that the
charge polarity and charge quantity of the toner on the
photosensitive member are controlled in the respective steps in
electrophotography and that a reversal development system is
employed.
It will be described by giving an example. When a negatively
chargeable photosensitive member and a negatively chargeable toner
are used, an image rendered visible is transferred to a transfer
medium in the transfer step by means of a transfer member having a
positive polarity, where the charge polarity of the transfer
residual toner varies from positive up to negative according to the
relation between the types of transfer mediums (differences in
thickness, resistance and dielectric constant) and the area of
images. However, the charging member having a negative polarity,
used to charge the negatively chargeable photosensitive member, can
uniformly adjust the charge polarity to the negative side even if
the polarity of the transfer residual toner has been shifted to the
positive side in the transfer step together with that of the
photosensitive member surface. Hence, when the reversal development
is employed as the developing system, the transfer residual toner,
which stands negatively charged, remains at light-area potential
portions to be developed, even though toner particles uniformly
charged in negative polarity at the time of development are present
on the photosensitive member surface. At dark-area potential
portions not to be developed, the toner is attracted toward the
toner carrying member due to the development electric field and
does not remain thereon.
However, in an attempt to form images at a higher process speed by
the use of the cleaning-at-development system, it is difficult to
charge the photosensitive member surface by means of the charging
member and also to uniformly adjust the charge polarity of the
transfer residual toner, in correlation with a decrease in charging
time per unit area of the photosensitive member. Hence, when the
reversal development is used as a development system, the transfer
residual toner present on the toner's dark-area potential portions
not to be developed can be attracted to the toner carrying member,
and is hard to collect by the aid of the development electric
field. Moreover, even if it has been collected on the toner
carrying member by mechanical force such as rubbing, the transfer
residual toner, unless its charge is not uniformly adjusted, may
adversely affect the charging performance of the toner present on
the toner carrying member, to cause a lowering of developing
performance.
The image forming method employing the cleaning-at-development
system is established by controlling the charge polarity of the
transfer residual toner simultaneously with the charging of the
photosensitive member. However, when the image forming method
employing the cleaning-at-development system is used in the
formation of images at such a higher process speed, it is hard for
the charge polarity of the transfer residual toner to be
controlled, tending to cause faulty collection at development.
Also, since the development itself is performed at a higher seed,
there is a problem that the charge of the transfer residual toner
collected at the developing step may more greatly affect the
developing performance to cause a lowering of developing
performance.
In addition, when the image forming method employing the
cleaning-at-development system is used in the formation of images
at a
high process speed, faulty charging tends to occur because of
contamination of the charging member.
Studies made by the present inventors have revealed that, when the
image forming method employing the cleaning-at-development system
is used in the formation of images at a high process speed of 120
mm/sec or above, or further 150 mm/sec or above, as the process
speed of a developing roller, the control of charge polarity must
be made more quickly in order to improve transfer residual toner
collection performance at the time of development, and, in order to
keep developing performance, the control of charge polarity of the
transfer residual toner must be made more surely and uniformly when
it passes through the charging member.
Especially in the so-called contact charging, in which the charging
member is brought into contact with the photosensitive member to
charge it, its charging mechanism utilizes electric discharge
according to the Paschen's law, where the adhesion of toner to the
charging member may seriously occur which is caused by the facts
that the charging member comes into contact with the photosensitive
member and the energy of electric discharge deteriorates the
toner.
In the cleaning system in which the transfer residual toner is
removed from the surface of the photosensitive member by means of a
cleaning member such as a blade or a fur brush, none of studies
have ever been made in consideration of any influence on the
charging of the toner present on the photosensitive member, the
performance of its collection to the developing assembly and the
developing performance of the toner collected to and reused in the
developing assembly.
Accordingly, the present inventors have made extensive studies on
various toners, and have discovered that, in the image forming
method employing the cleaning-at-development system, the
performance of charge control at the time the toner passes through
the charging member is closely concerned with the running
performance and image quality characteristics, and have discovered
especially that the incorporation of the compound represented by
Formula (A) into the toner brings about an improvement in the
performance of charge control at the time the toner passes through
the charging member.
EXAMPLES
The present invention will be specifically described below by
giving production examples and working examples. These by no means
limit the present invention. In the following formulation,
"part(s)" refers to "part(s) by weight" in all occurrences.
Toner Production
Example 1
Into a 2-liter four-necked flask having a high-speed stirrer
TK-type homomixer (manufactured by Tokushu Kika Kogyo), 710 parts
of ion-exchanged water and 450 parts of an aqueous 0.1 mol/liter
Na.sub.3 PO.sub.4 solution were introduced, and the mixture was
heated to 60.degree. C. with stirring by means of the high-speed
stirrer at a number of revolution adjusted to 10,000 rpm. Then, 68
parts of an aqueous 1.0 mol/liter CaCl.sub.2 solution was added
thereto slowly to prepare an aqueous dispersion medium containing
fine-particle slightly water-soluble dispersion stabilizer Ca.sub.3
(PO.sub.4).sub.2.
______________________________________ Styrene monomer 165 parts
n-Butyl acrylate monomer 35 parts Divinylbenzene monomer 0.5 part
Colorant (carbon black: bulk density: 370 g/cm.sup.3) 14 parts
Saturated polyester resin (terephthalic acid-propylene 10 parts
oxide modified bisphenol A; acid value: 15 mg KOH/g) Charge control
agent (compound No. 1) 2 parts Wax (ester compounds; m.p.:
70.degree. C.) 20 parts ______________________________________
Meanwhile, the above materials were dispersed for 3 hours by means
of an attritor (manufactured by Mitsui Mining & Smelting Co.,
Ltd.), followed by addition of 10 parts of a polymerization
initiator 2,2'-azobis(2,4-dimethylvaleronitrile) to obtain a
polymerizable monomer composition, which was then put into the
above aqueous dispersion medium to carry out granulation while
maintaining the number of revolution of the high-speed stirrer at
10,000 rpm. Thereafter, the reaction was carried out at 70.degree.
C. for 2 hours with stirring by means of paddle stirring blades,
and thereafter polymerization was carried out at 90.degree. C. for
10 hours.
After the reaction was completed, the suspension obtained was
cooled, and diluted hydrochloric acid was added thereto to remove
the slightly water-soluble dispersion stabilizer, followed by
filtration, water washing and drying, and further followed by air
classification to classify particles to the desired particle size,
thus colored particles (A) were obtained.
To 100 parts by weight of the colored particles (A), 1.5 parts of a
hydrophobic fine silica powder (BET specific surface area: 250
m.sup.2 /g) was dry-process mixed by means of a Henschel mixer
(manufactured by Mitsui Mining & Smelting Co., Ltd.) to obtain
toner (A) of the present invention.
In particle size distribution of the toner (A) as measured with
Coulter Counter Multisizer (manufactured by Coulter Co.), its
weight-average particle diameter (D4) was 6.8 .mu.m, number-average
particle diameter (D1) was 5.4 .mu.m, coefficient of variation was
26, and fine-powder content (the proportion of presence of 4.00
.mu.m or smaller particles in number distribution) was 16% by
number. Its shape factors SF-1 and SF-2 were 120 and 115,
respectively, and the value of (SF-2)/(SF-1) was 0.96.
Measurement with a flow type particle image analyzer FPIA-1000
(manufactured by Toa Iyou Denshi K.K.) revealed that the toner had
an average circularity (c) of 0.976 and a circularity standard
deviation (SDc) of 0.031. The proportion of particles having a
circularity of less than 0.950 was 13% by number.
The quantity of triboelectricity of the toner (A) was also measured
to find to be -45 mC/kg.
In the present invention, the quantity of triboelectricity of the
toner was measured by suction gauging. First, 0.5 g of the toner
and 9.5 g of a carrier (EFV-200/300, available from Powder Teck
Co.) were weighed out. These were put in a polyethylene container,
and left for 2 days in a measuring environment (23.degree. C./60%
RH). Thereafter, the container was hermetically stoppered, and
shaked 50 times to prepare a toner-carrier mix sample.
A charge quantity measuring device used in the present invention is
shown in FIG. 12. In its measuring container 42 made of a metal and
provided at the bottom thereof a conductive screen 43 of 500
meshes, having such an opening diameter that can capture the
carrier and remove only the toner by suction, 1.0 to 1.2 g of the
above mix sample are weighed out and put, and the container is
covered with a plate 44 made of a metal. Next, using a suction
device connected with the measuring container 42 via an insulating
portion, the sample is sucked for 1 minute from a suction opening
47 by operating an air-flow control valve 46 to control the
pressure indicated by a vacuum indicator 45 to be 250 mmH.sub.2 O.
Here, the charge quantity calculated from the voltage value V (V)
indicated by a potentiometer 49 and from the electrostatic capacity
C (.mu.F) of a capacitor 48 is divided by the weight W (g) of the
toner having been removed by suction, and the value obtained is
regarded as quantity of triboelectricity (mC/kg).
The state of the wax contained in toner particles of the toner (A)
was observed by TEM to confirm that it was encapsulated in
substantially a spherical form in such a state that it does not
dissolve in the binder resin and vice versa as diagrammatically
shown in FIG. 10A, and the value of (r/R).sub.st was 0.62.
7 parts of the toner (A) and 93 parts of a resin-coated magnetic
ferrite carrier (average particle diameter: 45 .mu.m) were blended,
thus a two-component developer (A) was also prepared.
Toner Production
Examples 2 to 4
Toners (B) to (D) and two-component developers (B) to (D) were
obtained in the same manner as in Toner Production Example 1 except
that the compound No. 1 and the carbon black were replaced with
charge control agents and colorants, respectively, shown in Table
3.
Toner Production
Example 5
Styrene-butyl acrylate copolymer resin (glass transition
temperature: 70.degree. C.) 100 parts
______________________________________ Colorant (carbon black used
in Toner Production Example 5 parts 1: bulk density: 370
g/cm.sup.3) Charge control agent (compound No. 1) 1 part Wax (low
molecular weight polypropylene; m.p.: 125.degree. C.) 4
______________________________________ parts
The above materials were mixed, and melt-kneaded by means of a
twin-screw extruder. The kneaded product obtained was cooled and
thereafter crushed using a hammer mill. The resultant crushed
product was pulverized by means of a jet mill, and the particles
obtained were further heated and made spherical, followed by
classification to obtain colored particles (E).
To 100 parts by weight of the colored particles (E), 1.5 parts of a
hydrophobic fine silica powder treated with hexamethyldisilazane
(BET specific surface area: 200 m.sup.2 /g) was dry-process mixed
by means of a Henschel mixer to obtain toner (E).
The wax in toner particles of the toner (E) was found to be
dispersed in a finely dispersed state, and the value of
(r/R).sub.st was 0.01 or below.
7 parts of the toner (E) and 93 parts of a resin-coated magnetic
ferrite carrier (average particle diameter: 45 .mu.m) were blended,
thus a two-component developer (E) was also prepared.
Toner Production
Examples 6 and 7
Toners (F) and (G) and two-component developers (F) and (G) were
prepared in the same manner as in Toner Production Example 1 except
that the compound No. 1 was used in an amount of 0.2 part and 7.0
parts, respectively.
Toner Production
Comparative Example 1
Comparative toner (a) and comparative two-component developer (a)
were obtained in the same manner as in Toner Production Example 5
except that the treatment to make the particles spherical by
heating was not made.
Toner Production
Comparative Example 2
Comparative toner (b) and comparative two-component developer (b)
were obtained in the same manner as in Toner Production Example 1
except that the compound No. 1 was replaced with 2 parts of an iron
complex salt of salicylic acid and the wax was replaced with 4
parts of an acid-modified polypropylene wax (m.p.: 125.degree.
C.).
The formulation of toner and various properties of toner in each
Production Example are shown in Table 3 (as Table 3A-3B).
Examples 1 to 7 &
Comparative Examples 1, 2
In these Examples and Comparative Examples, the image forming
apparatus as shown in FIG. 2 was used. As the developing assembly,
the one shown in FIG. 3 was used.
The photosensitive drum 1 comprises a substrate la and provided
thereon a photosensitive layer 1b having an organic
photo-semiconductor, and is rotated in the direction of an arrow.
By means of the charging roller 2 (the conductive elastic layer 2a
and the mandrel 2b) facing the photosensitive drum 1 and rotating
in contact with it, the surface of the photosensitive drum 1 is
electrostatically charged to have a surface potential of about -600
V. Exposure 3 is carried out using a polygon mirror by on-off
control on the photosensitive drum 1 in accordance with digital
image information, whereby an electrostatic latent image with an
exposed-area potential of -100 V and a dark-area potential of -600
V is formed. Using the developing assembly 4-1, a toner image is
formed on the photosensitive drum 1 by reversal development. The
toner image is transferred to the intermediate transfer member 5
(the elastic layer 5a and the mandrel 5b as a support). The toner
remaining on the photosensitive drum 1 after transfer is collected
in a residual toner container 9 by means of a cleaning member
8.
The intermediate transfer member 5 is comprised of the pipe-like
mandrel 5b and the elastic layer 5a provided thereon by coating,
formed of nitrile-butadiene rubber (NBR) in which carbon black
conductivity-providing agent has been well dispersed. The elastic
layer 5a thus formed has a hardness according to JIS K-6301, of 30
degrees and a volume resistivity of 10.sup.9 .OMEGA..multidot.cm.
Transfer electric current necessary for the transfer from the
photosensitive drum 1 to the intermediate transfer member 5 was
about 5 .mu.A, which was obtained by applying a voltage of +500 V
to the mandrel 5b from a power source.
The transfer roller 7 has an external diameter of 20 mm, and has an
elastic layer 7a formed by coating on a mandrel 7b of 10 mm
diameter, a foamable material of an ethylene-propylene-diene
terpolymer (EPDM) in which carbon black conductivity-providing
agent has been well dispersed. As the elastic layer 7a, the one
showing a volume resistivity of 10.sup.6 .OMEGA..multidot.cm and a
hardness according to JIS K-6301, of 35 degrees was used. A voltage
was applied to the transfer roller to flow a transfer current of 15
.mu.A.
In the heat fixing assembly H, a fixing assembly of a hot-roll type
having no function of oil application was used. Here, as both the
upper roller and the lower roller, those having surface layers of
fluorine resin were used, having roller diameter of 60 mm. The
fixing temperature was set at 160.degree. C., and the nip width at
7 mm.
Under the above conditions, a 10,000-sheet printing test was made
in an environment of normal temperature and normal humidity
(25.degree. C., 60% RH) at a printing rate of 12
sheets(A4-size)/minute in a monochromatic intermittent mode (i.e.,
a mode in which the developing assembly was made to pause for 10
seconds every time the images were printed on one sheet so that the
deterioration of the toner was accelerated by preliminary operation
of the developing assembly when again driven) while successively
supplying each of the two-component developers (A) to (G) and the
comparative two-component developers (a) and (b). Then, evaluation
on printed images thus obtained was made in respect of the items
shown later.
At the same time, the matching of the above developers to the image
forming apparatus used was also evaluated.
The transfer residual toner collected by cleaning was transported
to the developing assembly through the reuse mechanism, and
reused.
The results of the above evaluation are shown in Table 4.
Examples 1 to 4 show especially good results on the matching to
image forming apparatus. With regard to the reasons therefor, the
present inventors consider that in the present invention the shape
distribution of toner and the internal structure of toner have
precisely been controlled, and hence the following two points have
cooperatively acted, one being that the superior charge-providing
ability the charge control agent according to the present invention
has can readily be exhibited and the other being that the toner of
the present invention has restrained image forming apparatus from
contamination.
Example 8
In the present Example, a reuse mechanism was attached to a
commercially available laser beam printer LBP-EX (manufactured by
CANON INC.) to remodel the printer, which was again set up and
used. As a primary charging roller, a rubber roller (diameter: 12
mm; contact pressure: 50 g/cm) in which conductive carbon was
dispersed, and covered with a nylon resin, was used. On the
electrostatic latent image bearing member
(photosensitive drum), a dark-area potential V.sub.D of -700 V and
a light-area potential V.sub.L of -200 V were formed by laser
exposure (600 dpi). As the toner carrying member, a developing
sleeve whose surface was coated with a resin having carbon black
dispersed therein and had a surface roughness Ra of 1.1 was used,
where its surface movement speed was so set as to be 1.1 times the
movement speed of the photosensitive drum surface, and then the gap
(S-D distance) between the photosensitive drum and the developing
sleeve was set at 270 .mu.m. As the toner regulation member, a
blade made of urethane rubber was used in contact with the
developing sleeve. As the development bias, a bias formed by
superimposing an AC bias component on a DC bias component was used.
The fixing temperature of the heat-fixing assembly was set at
150.degree. C.
Under the above conditions, a 5,000-sheet printing test was made in
an environment of high temperature and high humidity (30.degree.
C., 80% RH) at a printing rate of 12 sheets(A4-size)/minute in an
intermittent mode (i.e., a mode in which the developing assembly
was made to pause for 30 minutes every time the images were printed
on 100 sheets so that the deterioration of the toner was
accelerated by preliminary operation of the developing assembly
when again driven) while successively supplying the toner (A).
Then, the printed images thus formed were evaluated to obtain good
image reproduction results that the image density was good and
stable and image fog little occurred.
The matching of the above toner to the image forming apparatus was
also good.
Example 9
In an environment of normal temperature and normal humidity
(25.degree. C., 60% RH), evaluation was made in the same manner as
in Examples 1 to 7 except that the developing assembly of the image
forming apparatus, shown in FIG. 3, was replaced with the one shown
in FIG. 4, the movement speed of the toner carrying member surface
was so set as to be 3.0 times the movement speed of the
electrostatic latent image bearing member surface, and images were
printed in a monochromatic intermittent mode (i.e., a mode in which
the developing assembly was made to pause for 1 minutes every time
the images were printed on one sheet so that the deterioration of
the toner was accelerated by preliminary operation of the
developing assembly when again driven) while successively supplying
the toner (A).
The toner carrying member used here had a surface roughness Ra of
1.5, and the toner regulation blade used was the one comprising a
phosphor bronze base plate to which urethane rubber was bonded and
the side coming into contact with the toner carrying member of
which was coated with nylon. Also, in the heat fixing assembly H, a
fixing assembly shown in FIGS. 5 and 6 was used. The surface
temperature of a temperature detector 31d of a heating element 31
(31a: heater substrate; 31b: heating element; 31c: surface
protective layer; 31d: temperature detector) was set at 140.degree.
C., the total pressure between the heating element 31 and a spongy
pressure roller 33 having a foam of silicon rubber in its lower
layer was set to be 8 kg, and the nip between the pressure roller
and a fixing film 32 was set to be 6 mm. As a fixing film 32, a 60
.mu.m thick heat-resistant polyimide film was used which had on its
side coming into contact with the transfer medium a low-resistance
release layer formed of PTFE (of a high-molecular-weight type)
having a conductive material dispersed therein. The results of
evaluation are summarized in Table 5.
Example 10
Using the image forming apparatus shown in FIG. 2, the
two-component developers (A) to (D) were put into the respectively
corresponding developing assemblies 4-1, 4-2, 4-3 and 4-4.
Full-color images were reproduced in an environment of 25.degree.
C. and 60% RH at a printing speed of 3 sheets(A4-size)/minute, and
images formed were evaluated. As a result, the matching to the
developing sleeve, photosensitive drum, intermediate transfer
member and fixing assembly was good, and full-color images having
good image characteristics were rerpoduced.
The evaluation items stated in Examples and Comparative Examples
and their evaluation criteria are as described below.
Printed-Image Evaluation
(1) Image density:
Evaluated on how image density was maintained when images were
printed on a prescribed number of sheets of usual plain paper (75
g/m.sup.2) for copying machines. The image density was measured
with MACBETH REFLECTION DENSITOMETER (manufactured by Macbeth Co.),
as relative density with respect to an image printed on a white
ground area with a density of 0.00 of an original.
A: 1.40 or more.
B: From 1.35 to less than 1.40.
C: From 1.00 to less than 1.35.
D: less than 1.00.
(2) Image fog:
Fog density (%) was calculated from a difference between the
whiteness at a white background area of images and the whiteness of
the recording medium to make evaluation on image fog, which was
measured with REFLECTOMETER (manufactured by Tokyo Denshoku Co.,
Ltd.).
A: Less than 1.5%.
B: From 1.5% to less than 2.5%.
C: From 2.5% to less than 4.0%.
D: More than 4.0%.
(3) Image blank areas:
A character pattern as shown in FIG. 13A was printed on a
cardboard, where evaluation was visually made by examining any
blank areas (the state shown in FIG. 13B) in character areas.
A: Blank areas little occur.
B: Slight blank areas are seen.
C: Blank areas are a little seen.
D: Conspicuous blank areas are seen.
Evaluation on Matching to Image Forming Apparatus
(1) Matching to developing sleeve:
After the printing test was finished, evaluation was visually made
by examining any sticking of the toner remaining on the developing
sleeve surface and how it affects printed images.
A: No sticking occurs.
B: Sticking little occurs.
C: Sticking is a little seen, but less affects images.
D: Sticking is greatly seen, and uneven images occur.
(2) Matching to photosensitive drum:
After the printing test was finished, evaluation was visually made
by examining any scratches on the photosensitive drum surface and
any sticking of the toner remaining thereon, and how they affect
printed images
A: None of them occurs.
B: Scratches are seen to slightly occur, but do not affect
images.
C: Sticking and scratches are seen, but less affect images.
D: Sticking is greatly seen, and faulty images occur as vertical
lines.
(3) Matching to intermediate transfer member:
After the printing test was finished, evaluation was visually made
by examining any scratches on the intermediate transfer member
surface and any sticking of the toner remaining thereon.
A: None of them occurs.
B: Scratches are seen to slightly occur, but do not affect
images.
C: Sticking and scratches are seen, but less affect images.
D: Sticking is greatly seen, and faulty images occur as vertical
lines.
(4) Matching to fixing assembly:
After the printing test was finished, evaluation was visually made
by examining any scratches on the fixing roller or fixing film
surface and any sticking of the toner remaining thereon.
A: None of them occurs.
B: Little occur.
C: Sticking and scratches are seen, but less affect images.
D: Sticking is greatly seen, and faulty images occur as vertical
lines.
Toner Production
Example 8
Into a 2-liter four-necked flask having a high-speed stirrer KUREA
MIX (manufactured by Emu Technique Co.), 700 parts of ion-exchanged
water and 800 parts of an aqueous 0.1 mol/liter Na.sub.3 PO.sub.4
solution were introduced, and the mixture was heated to 65.degree.
C. with stirring by means of the high-speed stirrer at a number of
revolution set to 15,000 rpm. Then, 70 parts of an aqueous 1.0
mol/liter CaCl.sub.2 solution was added thereto to prepare an
aqueous dispersion medium containing fine-particle slightly
water-soluble dispersion stabilizer Ca.sub.3 (PO.sub.4).sub.2. The
aqueous dispersion medium was reprepared by adding diluted
hydrochloric acid so that the pH of the aqueous dispersion medium
becomes 5.0.
Meanwhile, as a dispersoid, the following was used.
______________________________________ Styrene monomer 77 parts
2-Ethylhexyl acrylate monomer 23 parts Divinylbenzene monomer 0.2
part Colorant (carbon black: volatile: 1.0%) 5 parts Polycarbonate
resin (peak molecular weight: 7,500) 5 parts Charge control agent
(compound No. 1) 2 parts Ester wax A 7 parts
______________________________________
The ester wax A, and ester wax B used in Toner Production Example
12 described later were produced from the following long-chain
alkylcarboxylic acids and long-chain alkyl alcohols. Physical
properties of the ester waxes A and B are shown in Table 6.
Long-chain alkylcarboxylic acid components:
Palmitic acid (C.sub.16 H.sub.32 O.sub.2)
Stearic acid (C.sub.18 H.sub.36 O.sub.2)
Arachidic acid (C.sub.20 H.sub.40 O.sub.2)
Behenic acid (C.sub.22 H.sub.44 O.sub.2)
Lignoceric acid (C.sub.24 H.sub.48 O.sub.2)
Long-chain alkyl alcohol components:
Palmityl alcohol (C.sub.16 H.sub.34 O)
Stearyl alcohol (C.sub.18 H.sub.38 O)
Arachidyl alcohol (C.sub.20 H.sub.42 O)
Behenyl alcohol (C.sub.22 H.sub.46 O)
The above materials were dispersed for 3 hours by means of an
attritor, followed by addition of 7 parts of
2,2'-azobis(2,4-dimethylvaleronitrile) to prepare a polymerizable
monomer composition.
Next, the polymerizable monomer composition was put into the above
aqueous dispersion medium to carry out granulation with stirring
for 15 minutes in an atmosphere of N.sub.2 and internal temperature
of 70.degree. C. and while maintaining the number of revolution of
the high-speed stirrer at 15,000 rpm. Thereafter, the stirrer was
replaced with a stirrer having paddle stirring blades, and the same
temperature was maintained while stirring the system at 80 rpm. At
the time the polymerization conversion of the polymerizable monomer
composition reached 93%, an aqueous 0.1 mol/liter NaOH solution was
added to change the pH of the aqueous dispersion medium to 12. The
reaction temperature was further raised to 80.degree. C., and the
polymerization reaction was completed at the time the
polymerization conversion reached nearly 100%.
After the polymerization was completed, residual monomers were
evaporated off under reduced pressure, and then, after cooling,
diluted hydrochloric acid was added thereto to dissolve the
slightly water-soluble dispersion stabilizer. Washing with water
was further repeated several times, followed by drying by means of
a conical ribbon dryer (manufactured by Ohkawara Seisakusho), thus
colored particles (H) were obtained.
100 parts by weight of the colored particles (H) and 2 parts of a
hydrophobic oil-treated fine silica powder (BET specific surface
area: 200 m.sup.2 /g) were dry-process mixed by means of a Henschel
mixer (manufactured by Mitsui Mining & Smelting Co., Ltd.) to
obtain toner (H) of the present invention.
In particle size distribution of the toner (H), its weight-average
particle diameter (D4) was 6.5 .mu.m, coefficient of variation was
21, and fine-powder content was 10% by number. Its shape factors
SF-1 and SF-2 were 113 and 111, respectively, and the value of
(SF-2)/(SF-1) was 0.98. In its circularity frequency distribution,
the average circularity was 0.985 and the circularity standard
deviation was 0.026. The proportion of particles having a
circularity of less than 0.950 was 3% by number.
The state of the wax contained in toner particles of the toner (H)
was observed by TEM to confirm that it was encapsulated in
substantially a spherical form in such a state that it does not
dissolve in the binder resin and vice versa as diagrammatically
shown in FIG. 11A, and the value of (r/R).sub.st was 0.43.
Toner Production
Examples 9 to 14
Colored particles (I) to (N) were produced and then toners (I) to
(N) of the present invention were prepared in the same manner as in
Toner Production Example 8 except that the types and amount of the
charge control agent, colorant and wax and the pH of the aqueous
dispersion medium at the time of the polymerization reaction were
changed.
Toner Production
Comparative Examples 3 and 4
Comparative colored particles (c) and (d) were produced in the same
manner as in Toner Comparative Production Example 1 except that the
types of the charge control agent, colorant and wax were
changed.
100 parts by weight of each of the comparative colored particles
(c) and (d) and 2 parts of a hydrophobic oil-treated fine silica
powder (BET specific surface area: 200 m.sup.2 /g) were dry-process
mixed by means of a Henschel mixer to obtain comparative toners (c)
and (d), respectively.
Toner Production
Comparative Example 5
Comparative colored particles (e) were produced and then
comparative toner (e) was prepared in the same manner as in Toner
Production Example 8 except that 2 parts of a boron complex of
salicylic acid was used as the charge control agent, 4 parts of
modified polyethylene wax (m.p.: 115.degree. C.) was used as the
wax, and the pH of the aqueous dispersion medium at the time of
polymerization reaction was made constant.
Toner formulation and production conditions in each Toner
Production Example are shown in Table 7, and various properties of
the tones obtained are shown in Table 8.
Photosensitive Drum
Production Example
An aluminum cylinder of 30 mm diameter and 254 mm long was used as
a substrate, and layers with configuration as shown below were
successively formed thereon in layers by dip coating. Thus,
photosensitive drum (1) was produced.
(1) Conductive coating layer: Mainly composed of powders of tin
oxide and titanium oxide dispersed in phenol resin. Layer
thickness: 15 .mu.m.
(2) Subbing layer: Mainly composed of a modified nylon and a
copolymer nylon. Layer thickness: 0.6 .mu.m.
(3) Charge generation layer: Mainly composed of an azo pigment
having absorption in long wavelength range, dispersed in butyral
resin. Layer thickness: 0.6 .mu.m.
(4) Charge transport layer: Mainly composed of a hole-transporting
triphenylamine compound dissolved in polycarbonate resin (molecular
weight: 20,000 as measured by Ostwald viscometry) in weight ratio
of 8:10, and in which polytetrafluoroethylene powder (average
particle diameter: 0.2 .mu.m) was further added in an amount of 10%
by weight based on the total solid content and uniformly dispersed.
Layer thickness: 25 .mu.m.
The contact angle to water of the surface of Photosensitive Drum
(1) thus obtained was 95 degrees.
The contact angle was measured using pure water and using a contact
angle
meter Model CA-DS, manufactured by Kyowa Kaimen Kagaku K.K.
Example 11
As an image forming apparatus, a 600 dpi laser beam printer LBP-8
Mark IV (manufactured by CANON INC.) was made ready for testing.
This apparatus was remodeled, images were printed at a process
speed of 80 mm/sec and on 12 sheets per minute as LTR (letter) size
paper. As shown in FIG. 7, this apparatus has the following
process: The surface of the photosensitive member 56 (30 mm
diameter) is uniformly charged using the charging roller to which
DC and AC components have been applied. Here, the DC component is
controlled to a constant voltage and the AC component is controlled
to a constant current. Subsequent to the charging, images areas are
exposed to laser light 60 to form an electrostatic latent image,
which is then made into a visible image by the use of the toner 50
to form a toner image, and thereafter the toner image is
transferred to the transfer medium 58 by means of the transfer
roller 57 to which a voltage has been applied.
Next, the developing assembly 52 of the process cartridge was also
modified in the following way: In place of the toner feeding member
aluminum sleeve internally provided with a magnet, a
medium-resistance rubber roller (diameter: 16 mm) formed of
silicone rubber whose resistance had been controlled by dispersing
carbon black in it was used as the toner carrying member 54 and was
brought into contact with the photosensitive member 56. The toner
carrying member 54 was so driven that the movement of its surface
was in the same direction as that of the surface of the
photosensitive member 56 at the former's part coming into contact
with the latter and its rotational peripheral speed was 150% with
respect to the rotational peripheral speed of the photosensitive
member; i.e., the toner carrying member was rotated at a peripheral
speed of 120 mm/sec, and at a relative peripheral speed of 40
mm/sec with respect to the surface of the photosensitive
member.
As a means for coating the toner on the toner carrying member, the
toner coating roller 55 was provided inside the developer container
and was brought into contact with the toner carrying member. The
toner coating roller 55 was so rotated that the movement direction
of its surface was opposite to the movement direction of the
surface of the toner carrying member at the contact part, and in
this way the toner was coated on the toner carrying member. Also,
for the purpose of coat layer control of the toner on the toner
carrying member, a resin-coated blade 53 made of stainless steel
was attached. As the cleaning member 59, a blade made of urethane
rubber was used.
The photosensitive drum (1), produced in Photosensitive Drum
Production Example 1, was used as the photosensitive member and the
toner (H) was used as the toner. Process conditions were so set as
to provide the following development conditions.
Photosensitive member dark-area potential: -700 V
Photosensitive member light-area potential: -150 V
Development bias: -450 V (DC component only)
A 2,000 sheet continuous printing test was made in an environment
of normal temperature and normal humidity (25.degree. C., 60% RH)
while supplying the toner. Thereafter, the evaluation environment
was changed to an environment of high temperature and high humidity
(30.degree. C., 80% RH) to make a further 3,000 sheet printing
test, and printed images were evaluated. As a result, good results
were obtained on all of image density, prevention of black spots
around line images, prevention of image blank areas, prevention of
fog, and dot reproducibility. Also, any faulty cleaning did not
occur, and the image quality equal to that of initial stage was
attained. After the printing test was completed, the surfaces of
the developing roller, photosensitive member and fixing assembly
were examined, but no melt-adhesion of toner was seen, and it was
unnecessary to change them for new ones.
The results of evaluation are shown in Table 9.
Example 12
The procedure of Example 11 was repeated except the following.
The toner carrying member was so driven that the movement of its
surface was in the same direction as that of the surface of the
photosensitive member at the former's part coming into contact with
the latter and its rotational peripheral speed was 200% with
respect to that of the photosensitive member; i.e., the toner
carrying member was rotated at a peripheral speed of 160 mm/sec,
and at a relative peripheral speed of 80 mm/sec with respect to the
surface of the photosensitive member.
Process conditions were so set as to fulfill the following
development conditions.
Development bias: -500 V (DC component only)
A continuous printing test was made in the same manner as in
Example 11. As a result, though slightly inferior to Example 11
because of severer conditions due to a higher process speed, good
results were obtained on the whole. Any faulty cleaning also did
not occur, and the image quality equal to that of initial stage was
attained. After the printing test was completed, the surfaces of
the developing roller, photosensitive member and fixing assembly
were examined, but no melt-adhesion of toner was seen, and it was
unnecessary to change them for new ones.
The results of evaluation are shown in Table 9.
Examples 13 to 18
Printing tests were made in the same manner as in Example 11 except
for using the toners (I) to (N), respectively, as the toner.
Evaluation was made similarly. As the result, as shown in Table 9,
good results were obtained on the whole.
Comparative Examples 3 to 5
Printing tests were made in the same manner as in Example 11 except
for using the comparative toners (c) to (e), respectively, as the
toner. Evaluation was made similarly. The results of evaluation are
shown in Table 9.
The evaluation items stated in Examples 11 to 18 and Comparative
Examples 3 to 5 and their evaluation criteria are as described
below.
Printed-Image Evaluation
(1) Image density:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(2) Spots around line images:
This is evaluation on spots around fine line images, concerning
image quality of graphical images. Evaluation was visually made by
examining the reproducibility of line images and any spots of toner
around line images formed when one-dot line images tending to cause
spots around line images than character images were printed on
plane paper (75 g/m.sup.2).
A: Spots around line images little occur, showing a good line
reproducibility.
B: Very slight black spots around line images are seen.
C: Spots around line images are slightly seen, less affect line
reproducibility.
D: Conspicuous black spots around line images are seen, showing a
poor line reproducibility.
(3) Image blank areas:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(4) Image fog:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(5) Dot reproducibility:
Images of a pattern of isolated dots of small diameter (50 .mu.m
each) as shown in FIG. 14, which tend to form closed electric
fields on account of latent image electric fields and are difficult
to reproduce, were printed and the reproducibility of the dots was
evaluated.
A: Missing dots are 2 or less per 100 dots.
B: Missing dots are 3 to 5 per 100 dots.
C: Missing dots are 6 to 10 per 100 dots.
D: Missing dots are 11 or more per 100 dots.
Evaluation on Matching to Image Forming Apparatus
(1) Matching to developing roller:
After the printing test was finished, evaluation was visually made
by examining any sticking of the toner to the developing roller
surface and how it affects printed images.
A: No sticking occurs.
B: Contamination a little occurs, but sticking little occurs.
C: Sticking occurs, but less affect images.
D: Sticking greatly occurs, and uneven images occur.
(2) Matching to photosensitive member:
Evaluated according to the evaluation criteria for the matching
evaluation in Example 1.
(3) Matching to fixing assembly:
Evaluated according to the evaluation criteria for the matching
evaluation in Example 1.
Example 19
Images were formed in the same manner as in Example 11 except that,
in the image forming apparatus used therein, the toner coating
roller 55 in the developing assembly 52 was replaced with a sponge
roller constituted of a single layer and a bias voltage was applied
to the toner coating roller 55 from a bias applying means (not
shown).
In this development, only a DC component of -300 V was applied as
the development bias voltage to the developing roller 54, and only
a DC component of -450 V was applied as the coating bias voltage to
the toner coating roller 55.
Evaluation was made in the same manner as in Example 11. As a
result, the image density and the prevention of image fog were both
stable and good, any faulty cleaning did not occur, and good image
quality was attained. The matching to image forming apparatus was
also good.
Example 20
Images were formed by using the toner (H) in the developing
assembly 4-4 of the image forming apparatus shown in FIG. 2.
In the image forming apparatus, as shown in FIG. 2, a cleaner
having a cleaning member coming into contact with the
photosensitive member surface as a first cleaning means for
removing the toner remaining on the photosensitive member surface
after primary transfer is provided between the primary-transfer
zone and the charging zone where the photosensitive member is
charged, and a cleaner having a cleaning member coming into contact
with the intermediate transfer member surface as a second cleaning
means for removing the toner remaining on the intermediate transfer
member surface after secondary transfer is provided on the
downstream side of the secondary-transfer zone and the downstream
side of the primary-transfer zone.
As the developing assembly 4-4, a developing assembly constituted
like the developing assembly 78 shown in FIG. 9 was used.
A medium-resistance rubber roller (diameter: 16 mm) formed of
silicone rubber whose resistance had been controlled by dispersing
carbon black in it was used as the toner carrying member 79 and was
brought into contact with the photosensitive member surface. The
toner carrying member 79 was so driven that the movement of its
surface was in the same direction as that of the surface of the
photosensitive member surface at the former's part coming into
contact with the latter and its rotational peripheral speed was
150% with respect to the rotational peripheral speed of the
photosensitive member. Namely, the toner carrying member was
rotated at a peripheral speed of 120 mm/sec and at a relative
peripheral speed of 80 mm/sec with respect to the surface of the
photosensitive member.
As a means for coating the toner on the toner carrying member, a
sponge roller constituted of a single layer was provided as the
toner coating roller 82 and was brought into contact with the toner
carrying member. The toner coating roller 82 was so rotated that
the movement direction of its surface was opposite to the movement
direction of the surface of the toner carrying member at the
contact part, and in this way the toner was coated on the toner
carrying member. Also, for the purpose of coat layer control of the
toner on the toner carrying member, a resin-coated blade 86 made of
stainless steel was attached.
The photosensitive drum (1), produced in Photosensitive Drum
Production Example 1, was used as the photosensitive member. Image
forming conditions were so set as to fulfill the following
development and transfer conditions.
Photosensitive member dark-area potential: -700 V
Photosensitive member light-area potential: -150 V
Development bias applied to the toner carrying member: -450 V (DC
component only)
Coating bias applied to the toner coating roller: -300 V (DC
component only)
Transfer bias applied to the intermediate transfer member in the
primary transfer step: 300 V (DC component only)
Transfer bias applied to the transfer roller in the secondary
transfer step: 1,000 V (DC component only)
Under the above image forming conditions, toner images transferred
to transfer mediums were heat-fixed to the recording mediums by
means of the following heat fixing assembly.
As the heat fixing assembly H, a fixing assembly of a heat roll
system having no function of oil application was used. Here, the
fixing assembly used had fluorine resin surface layers on both the
upper roller and the lower roller, and the rollers each had a
diameter of 60 mm. The fixing temperature was set at 150.degree.
C., and the nip width in 7 mm.
Using the image forming apparatus constituted as described above, a
5,000 sheet continuous printing test was made. As a result,
high-quality images with high density and free of image stains were
obtained.
The matching to image forming apparatus was also good.
Example 21
As the image forming apparatus shown in FIG. 7, a 600 dpi laser
beam printer LBP-860 (manufactured by CANON INC.) was made ready
for testing. The printer was modified on the following points and
remodeled into an apparatus employing the cleaning-at-development
system.
From the process cartridge, the cleaning rubber blade was detached.
The charging system was changed for the contact charging system in
which a rubber roller is brought into contact, and a voltage of a
DC component (-1,400 V) was applied, and the process speed was
changed to 94 mm/sec. Correspondingly to the process speed made
higher, conditions are set severer for uniform charging of the
photosensitive member.
The photosensitive drum (1) was used as the photosensitive
member.
Next, the developing part of the process cartridge was modified. A
medium-resistance rubber roller (diameter: 16 mm; hardness: ASKER C
45 degrees; resistance: 10.sup.5 .OMEGA..multidot.cm) formed of
foamed urethane was used in place of the toner carrying member
stainless steel sleeve, and was brought into contact with the
photosensitive member. The toner carrying member was so driven that
the movement of its surface was in the same direction as that of
the surface of the photosensitive member at the former's part
coming into contact with the latter and its rotational peripheral
speed was 130% with respect to the rotational peripheral speed of
the photosensitive member.
As a means for coating the toner on the toner carrying member, a
toner coating roller was provided in contact with the toner
carrying member in the developing part. Also, for the purpose of
coat layer control of the toner on the toner carrying member, a
resin-coated blade made of stainless steel was attached. The
development bias applied to the toner carrying member at the time
of development was changed to a DC component (-450 V) only.
The image forming apparatus was so modified and process conditions
were so set as to fit such modification of the process
cartridge.
With regard to the charge potential of the photosensitive member,
its dark-area potential was set at -800 V, and light-area potential
at -150 V. Paper of 75 g/m.sup.2 in basis weight was used as
transfer mediums.
Using the toner (H), character images with a printed area
percentage of 4%
were continuously printed on 100 sheets in an environment of normal
temperature and normal humidity (25.degree. C., 60% RH), and
thereafter, images were evaluated and any image stains due to
faulty charging were examined. As a result, good results were
obtained on all of image density, prevention of image stains,
transfer performance, prevention of fog, and dot reproducibility.
The quantity (mg) of toner adhering to the charging roller per unit
surface area (cm.sup.2) was also measured to find that it was as
very small as 0.01 mg/m.sup.2. After the evaluation at the initial
100-sheet printing was completed, images were continuously printed
on further 2,000 sheets, and images were again evaluated, whereupon
the same image quality as that of initial stage was attained. Also,
the photosensitive member and the developing roller were both
observed, where any melt-adhesion of toner did not occur, and it
was unnecessary to change them for new ones.
The results of evaluation are shown in Table 10.
Example 22
Evaluation was made in the same manner as in Example 21 except that
the process speed was made higher to 120 mm/sec. As the result,
though slightly inferior to Example 21 because of severer
conditions due to a higher process speed, good results were
obtained on the whole.
Examples 23 to 25
Printing tests were made in the same manner as in Example 21 except
for using the toners (L) to (N), respectively, as the toner.
Evaluation was made similarly. The results are shown in Table
10.
Comparative Examples 6 to 8
Printing tests were made in the same manner as in Example 21 except
for using the comparative toners (c) to (e), respectively, as the
toner. Evaluation was made similarly. The results are shown in
Tnable 10.
In Comparative Examples 6 and 7, which made use of toners not
satisfying the specific shape of the present invention, the toner
came to seriously adhere to the charging roller surface with
progress of running, and the tests were stopped halfway because it
was difficult to continue the 2,000-sheet continuous printing
tests.
The evaluation items stated in Examples 21 to 25 and Comparative
Examples 6 to 8 and their evaluation criteria are as described
below.
Printed-Image Evaluation
(1) Image density:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(2) Image stains:
A halftone image constituted of one-dot lines and one-dot spaces
was printed on plane paper (75 g/m.sup.2), where evaluation was
visually made by examining occurrence of any image stains.
A: No stain occurs.
B: Stains are slightly seen.
C: Stains in fine black spots are seen.
D: Periodical belt-like stains or vertical-line stains are
seen.
(3) Image blank areas:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(4) Image fog:
Evaluated according to the evaluation criteria for the image
evaluation in Example 1.
(5) Dot reproducibility:
Evaluated according to the evaluation criteria for the image
evaluation in Example 11.
Charging Roller Toner Adhesion
The quantity of the toner per unit area having adhered to the
charging roller per unit surface area was measured. The less the
quantity of the toner adhering is, the better it is meant to
be.
A: Less than 0.20 mg/cm.sup.2.
B: From 0.20 mg/cm.sup.2 to less than 0.35 mg/cm.sup.2.
C: From 0.35 mg/cm.sup.2 to less than 0.55 mg/cm.sup.2.
D: More than 0.55 mg/cm.sup.2.
Evaluation on Matching to Image Forming Apparatus
(1) Matching to developing roller:
Evaluated according to the evaluation criteria for the matching
evaluation in Example 11.
(2) Matching to photosensitive member:
Evaluated according to the evaluation criteria for the matching
evaluation in Example 1.
(3) Matching to fixing assembly:
Evaluated according to the evaluation criteria for the matching
evaluation in Example 1.
TABLE 1
__________________________________________________________________________
No. M R.sub.1 and R.sub.4 R.sub.2 and R.sub.3 X.sup.n+
__________________________________________________________________________
1 B #STR15## KSTR16## .sup.+ - 2 B H-- 17## #STR18## - 3 B H-- 19##
#STR20## - 4 B #STR21## Mg.sup.2+ - 5 B CH.sub.3 -- Zn.sup.2+ - 6
Cr #STR24## #STR25## #STR26## - 7 Co H-- 27## #STR28## - 8 Co
n-C.sub.12 H.sub.25 -- #STR30## - 9 Al H-- 31## #STR32## - 10 Al
CH.sub.3 -- ##STR34##
__________________________________________________________________________
TABLE 2
__________________________________________________________________________
No. M R.sub.1 and R.sub.4 R.sub.2 and R.sub.3 X.sup.n+
__________________________________________________________________________
11 Ti CSTR35## .sub.2 H.sub.5 -- #STR36## - 12 Ti #STR37## #STR38##
#STR39## - 13 Ni #STR40## H.sup.+ - 14 Fe CH.sub.3 -- #STR43## - 15
Fe H-- 44## ##STR45##
__________________________________________________________________________
TABLE 3A
__________________________________________________________________________
Toner formulation Charge control agent Colorant (1) Shape factors
Toner (pbw) (pbw) (pbw) SF-1 SF-2 (SF-2)/(SF-1)
__________________________________________________________________________
Toner Production Example: 1 Toner (A) Compound No. 1 (1) Carbon
black (7) 1 120 115 0.96 2 Toner (B) Compound No. 1 (1) C.I. P.Red
1 (5) 1 121 118 0.98 3 Toner (C) Compound No. 1 (1) C.I. P.Bl 2 (5)
1 121 110 0.91 4 Toner (D) Compound No. 9 (1) C.I. P.Yl 16 (5) 1
127 117 0.92 5 Toner (E) Compound No. 14 (1) Carbon black (5) 1 120
136 1.13 6 Toner (F) Compound No. 1 (0.1) Carbon black (7) 0.1 130
130 1.00 7 Toner (G) Compound No. 1 (3.5) Carbon black (7) 3.5 150
130 0.86 Toner Production Comparative Example: 1 Toner (a) Compound
No. 1 (1) Carbon black (5) 1 164 143 0.87 2 Toner (b) Salicylic
acid Carbon black (7) 1 132 125 0.95 iron complex (1)
__________________________________________________________________________
(1): Amount of charge control agent per 100 parts by weight of the
binder resin P. Red.: Pigment Red P.Bl: Pigment Blue P.Yl: Pigment
Yellow Remarks: In the table, the toner formulation is expressed as
the amount per 100 parts by weight as total parts by weight of the
polymerizable monomer or total parts by weight of the binder
resin.
TABLE 3B
__________________________________________________________________________
(* by number) Coulter Counter FPIA circularity particle size
distribution frequency distribution Weight = Number = Circu-
average average Coeffi- Circu- larity particle particle Fine =
cient Average larity less State of Quantity diameter diameter
powder of circu- standard than presence of tribo- D4 D1 content
varia- larity deviation 0.950 of wax electricity (.mu.) (.mu.m)
(%)* tion c SDc (%)* (r/R)st (mC/kg)
__________________________________________________________________________
Toner Production Example: 1 6.8 5.4 16 22 0.976 0.031 13 Spherical
-45 0.62 2 7.2 5.5 10 23 0.973 0.030 12 Spherical -42 0.59 3 6.9
5.8 15 22 0.974 0.030 15 Spherical -50 0.63 4 7.5 6.2 10 21 0.971
0.033 19 Spherical -37 0.60 5 7.0 6.2 22 31 0.972 0.037 25 Fine
dis- -43 persion .ltoreq.0.01 6 7.0 6.0 10 24 0.966 0.034 20
Spherical -10 0.55 7 6.9 6.5 12 23 0.945 0.037 33 Spherical -75
0.48 Toner Production Comparative Example: 1 7.1 5.6 31 33 0.928
0.059 59 Fine dis- -34 persion .ltoreq.0.01 2 6.9 5.7 32 26 0.970
0.036 21 Fine dis- -26 persion 0.03
__________________________________________________________________________
TABLE 4
__________________________________________________________________________
Evaluation of matching to image forming apparatus Evaluation of
printed images Inter- Image density Image Devel- Photo- mediate
Initial 1,000 5,000 10,000 Image blank oping sensitive transfer
Fixing Developer stage sheets sheets sheets fog areas sleeve drum
member assembly
__________________________________________________________________________
Example: 1 (A) A A A A A A A A A A 2 (B) A A A A A A A A A A 3 (C)
A A A A A A A A A A
4 (D) A A A A A B A A A A 5 (E) A A B C C C C C C C 6 (F) B B B C C
B B C B A 7 (G) A A B B B C B B C B Comparative Example: 1 (a) A B
C D D D D C C D 2 (b) C A B C C C D D C B
__________________________________________________________________________
TABLE 5
__________________________________________________________________________
Evaluation of matching Evaluation of printed images to image
forming apparatus Image density Photo- Initial 1,000 5,000 10,000
Image Developing sensitive Fixing Toner stage sheets sheets sheets
fog sleeve drum assembly
__________________________________________________________________________
Example: 9 (A) A A A A A A A A
__________________________________________________________________________
TABLE 6
__________________________________________________________________________
Content of ester compounds (% by weight) Melting Ester Total number
of carbon atoms of ester compounds point Hard- wax C.sub.32
C.sub.34 C.sub.36 C.sub.38 C.sub.40 C.sub.42 C.sub.44 C.sub.46
Others (.degree. C.) ness Mw Mn
__________________________________________________________________________
A 0 0 0 0.3 6.1 16.5 74.9 0.6 1.6 74.4 1.8 630 500 B 0 0 5.2 5.8
13.8 27.0 40.0 2.7 5.5 72.9 1.3 590 480
__________________________________________________________________________
TABLE 7
__________________________________________________________________________
* at switching Production conditions 1st Polymer-* 2nd Charge
control agent Wax Colorant reac- ization reac- Amt. Amt. Amt. tion
conver- tion Toner Type (pbw) Type (pbw) Type (pbw) pH sion pH
__________________________________________________________________________
Toner Production Example: 8 Toner (H) Compound No. 1 2 Ester 7
Carbon 7 5.0 93 12 wax A black 9 Toner (I) Compound No. 1 2 Ester 7
C.I. 5 5.0 95 12 wax A P.Red 1 10 Toner (J) Compound No. 1 2 Ester
7 C.I. 5 5.0 90 12 wax A P.Bl 2 11 Toner (K) Compound No. 1 2 Ester
7 C.I. 5 5.5 85 11 wax A P.Yl 16 12 Toner (L) Compound No. 6 3
Ester 7 Carbon 7 5.3 80 12 13 Toner (M) Compound No. 9 1 wax B
black Paraffin 30 Carbon 7 6.2 56 10 wax black (mp:70.degree. C.)
14 Toner (N) Compound No. 9 1 Modified 4 Carbon 7 8.3 15 9
polyethyl- black ene wax (mp:115.degree. C.) Toner Production
Comparative Example: 3 Toner (c) Compound No. 1 2 Paraffin 7 Carbon
7 -- -- -- wax black (mp:70.degree. C.) 4 Toner (d) Compound No. 1
2 Paraffin 7 Carbon 7 -- -- -- wax black (mp:70.degree. C.) 5 Toner
(e) Salicylic acid 2 Modified 4 Carbon 7 9.0 -- -- boron complex
polyethyl- black ene wax (mp:115.degree. C.)
__________________________________________________________________________
(P.Red.: Pigment Red, P.Bl: Pigment Blue, P.Yl: Pigment Yellow
TABLE 8
__________________________________________________________________________
(* by number) FPIA particle size Coulter Counter distribution
particle size distribution Circu- Weight = Coeffi- Circu- larity
average Fine = cient Aver- larity less State of Shape particle
powder of age standard than presence (1) factors diameter content
varia- circu- devia- 0.950 of wax Toner (pbw) SF-1 SF-2 (.mu.m)
(%)* tion larity tion (%)* (r/R)st
__________________________________________________________________________
Toner Production Example: 8 (H) 2 113 111 6.5 10 21 0.985 0.026 3
Spherical 0.43 9 (I) 2 116 114 6.3 12 22 0.980 0.029 7 Spherical
0.41 10 (J) 2 107 106 6.1 9 20 0.989 0.020 1 Spherical 0.44 11 (K)
2 129 118 6.9 17 24 0.973 0.033 9 Spherical 0.39 12 (L) 3 142 125
7.2 20 26 0.964 0.034 14 Spherical 0.33 13 (M) 1 148 129 7.4 21 26
0.952 0.036 26 Spherical 0.79 14 (N) 1 155 138 7.3 23 29 0.946
0.038 32 Spherical 0.08 Toner Production Comparative Example: 3 (c)
2 155 146 6.4 26 32 0.926 0.061 64 Fine dispers. .ltoreq.0.01 4 (d)
2 172 153 6.2 29 34 0.931 0.057 55 Fine dispers. .ltoreq.0.01 5 (e)
2 148 141 7.0 22 27 0.943 0.037 40 Fine dispers. 0.03
__________________________________________________________________________
(1): Amount of charge control agent per 100 parts by weight of the
binder resin
TABLE 9
__________________________________________________________________________
After 3,000-sheet image reproduction in H/H After 2,000-sheet
(after 5,000 sheets in total) image reproduction Evaluation of
matching in N/N to image forming apparatus Evaluation of Evaluation
of Photo- printed images printed images Developing sensitive Fixing
Toner (1) (2) (3) (4) (5) (1) (2) (3) (4) (5) roller drum assembly
__________________________________________________________________________
Example: 11 Toner (H) A A A A A A A A A A A A A 12 Toner (H) A A A
A A A B B A B A A A 13 Toner (I) A A A A A A A A A A A A A 14 Toner
(J) A A A A A A A A A A A A A 15 Toner (K) A A A B B A B A A B A A
A 16 Toner (L) B B B B B B B B C B B B B 17 Toner (M) B B B C B B C
C C C B C B 18 Toner (N) B B C C C B C C C C C C C Comparative
Example: 3 Toner (c) C C C C D D D D D D C D D 4 Toner (d) C C C C
C C D D D D D C D 5 Toner (e) B B B C C C C C D C D D C
__________________________________________________________________________
N/N: Normal temperature/normal humidity environment H/H: High
temperature/high humidity environment (1): Image density (2): Spots
around line images (3): Image blank areas (4): Image fog (5): Dot
reproducibility
TABLE 10
__________________________________________________________________________
After 2,000-sheet image reproduction After 100-sheet Evaluation of
matching image reproduction to image forming apparatus Evaluation
of Evaluation of Photo- printed images printed images Developing
sensitive Fixing Toner (1) (2) (3) (4) (5) (6) (1) (2) (3) (4) (5)
roller drum assembly
__________________________________________________________________________
Example: 21 (H) A A A A A A A A A A A A A A 22 (H) A A A A A B A A
A B B A A A 23 (L) B B B B B B B B B C B B B B 24 (M) B B B C C A B
C C C C B C B 25 (N) B B B C C C B C B C C B C C Comparative
Example: 6 (c) B B C C C D -- -- -- -- -- -- -- -- 7 (d) C C B D C
D -- -- -- -- -- -- -- -- 8 (e) C B B C C C B C C D C D D C
__________________________________________________________________________
(1): Image density (2): Image stains (3): Image blank areas (4):
Image fog (5): Dot reproducibility (6): Charging roller toner
adhesion
* * * * *